Flying disc

A flying disc is a flat round object with a thick rim. The rim make the disc easier to grip and throw, and also keeps the disc from turning over as it flies. Detailed throwing instructions are below, but the basic goal is to throw the disc while also making the disc spin. 
Also mentioned below is a flying ring, made under the brand name Aerobie. Although these designs are very different, they both use air resistance in the same way to fly.
Unlike the Aerobie, flying discs are used in both Ultimate Frisbee and Disc Golf. The Frisbee brand of flying disc is rarely used in official competition in either game, which is why the team sport of Ultimate Frisbee is officially called simply "Ultimate." Still, as "Kleenex" was once a word used to mean "facial tissue," "Frisbee" is still broadly used as a synonym for a flying disc.
The Aerobie.
The Aerobie Superdisk is an alternative design of flying disc that, although somewhat differently shaped, still has very similar properties to the conventional disc. It has less air resistance. Because there is less resistance to motion, the Aerobie discs can fly farther than the conventional disc. The Aerobie flying ring has minimal drag and holds the world record for the longest flight by a human-thrown projectile. However, due to the lack of a rim, the Aerobie is less suited to angled, curved flights and air-bouncing.
Spin of the disc.
The spin of the disc helps to keep the disc stable in flight and prevent unplanned tilting. This is because a large angular momentum stabilises the disc in the same way that it keeps a gyroscope steady, with the angular force forcing the mass of the disc away from the centre of mass, perpendicular to the axis of rotation. Any unequal force acting on a particular area of the disc is quickly redirected to be equal over the circumference of the disc.
As the disc spins faster, it becomes more stable due to the rapidity of the equalisation of forces.
Mass of the disc.
The force required to accelerate the disc is directly proportional to the mass of the disc. This decreases the acceleration of the disc, assuming that the force of projection is constant. Therefore, discs come in a variety of weights, although those used for Ultimate are mainly 175 g in mass, heavier than the majority of discs and considerably heavier than an aerobie.
Flying discs (including Frisbees) can be thrown in many ways. All involve spinning the disc to give it gyroscopic stability, and accelerating its mass to a certain velocity. Without spin, a disc will wobble and fall; without velocity, the disc will not go anywhere. Using these two guidelines, any number of throws are possible. Most discs are designed to create lift when thrown with the flat side up.
Techniques.
Right-side up.
Right-side up throws are all similar in that they react the same way to the tilt of the disc when it is released. A disc thrown right-side up will accelerate in the direction of the low end of the disc. A disc tilted leading-edge up will lose speed at the end of the throw and make a gentle landing; if tilted sideways (known in aeronautics terms as roll), it can curve around objects.
There is a language for describing throws that curve. Both descriptions are relative to the direction the person is facing and intends to throw. This axis is marked in "red" in the picture.
Backhand.
This is probably the most commonly learned throw, and also one of the most powerful. 
Forehand.
This throw is also known as the "flick," "two-finger," or the "side-arm". Focused in the wrist, this throw takes little time to execute. Along with the backhand, it is one of the two most common throws used in Ultimate.
Variations.
The forehand is a versatile throw, and can be adapted to many different situations.
Push Pass.
The Push Pass: A relatively little-used throw, it is thrown with a grip similar to a backhand (index finger on the outer rim of the disc, thumb on top, other fingers curled underneath) but is released on the forehand side from a forehand stance. A pronating wrist snap similar to a forehand release pushes the disc forward, while spin is imparted "backwards" by rolling the disc off the index finger. A final flick of the index finger finishes the release. It is difficult to impart as much spin to the push pass as one can typically impart to a forehand or backhand, resulting in a less stable throw. It is useful in Ultimate for very short throws released to the forehand side.
Thumber forehand.
The thumber forehand is also known as a The Beach Thumber, Peach, or in the sport of guts, simply as a thumber. Its primary advantage is that it can be thrown quite hard and with a great amount of spin, and is relatively easy to learn. It is often seen used in a game of Guts due to its power and velocity. It is unpopular in Ultimate due to several disadvantages when compared to the standard forehand. It is relatively difficult to impart different curves or release angles to, it is harder to release extended away from the thrower's body, and it makes for slow grip transitions to a backhand or hammer.
Overhand.
The Overhand (also known as "Hungarian", "flamingo", "dragonwing", "windmill", "waffle", "discus", "wrist-hook", "chicken wing", or "biscuit") is rarely used among ultimate players, because the alternative, the traditional forehand, allows greater sideways arm extension, useful in moving the disc around defenders. The Overhand is most useful when the disc is caught above the head and must be thrown quickly without changing grips, such as during a Greatest attempt.
Duck.
The Duck (also known as a "bear claw", a "duder," or a "useless") is thrown with a similar grip to the Overhand, except it is the backward version of it. While the Overhand is thrown with counter-clockwise spin (for right-handers), the duck is thrown with clockwise spin. It is usually thrown with the arm out to the side or above the head. It is called the duck due to the shape of the gripping hand during the throw, as if making a duck shadow puppet. This throw is used in attempts at The Greatest (jumping out of bounds and throwing the Frisbee back in to play while in the air).
Upside-down.
A disc thrown upside-down has a very different flight path than one thrown right-side up. The lift force does not enforce stable flight as it does on a right-side up disc, resulting in a more of a parabolic arc in flight. As with a right-side up throw, however, the flight path of the disc will curve toward the lower edge. This banking effect is most pronounced when the disc is at a 45 degree angle, and less pronounced when it is near-vertical, or near-horizontal. 
Gyroscopic precession causes the disc to rotate toward horizontal through its flight path. Unlike a right-side up throw, however, an upside-down disc will not precess toward a stable flat state, and will in stead oscillate past horizontal and begin to bank in the opposite direction. This shuttlecock-like effect is known as "helixing", and is generally avoided due to the difficulty in controlling a helixing flight path. For this reason, an upside down throw is typically released with either clockwise rotation and the left edge up, or counterclockwise rotation and the right edge up. The longer the disc is expected to remain in the air, the closer to vertical it must be at release to avoid the helixing effect.
Hammer.
The Hammer is gripped just like a normal forehand throw, and is generally a mid-range, high and arching throw.
A hammer, when thrown by a right-handed thrower, will arc up and to the left as it moves away from the thrower, and will bank towards the right in flight. The banking effect will be more pronounced if the disc is thrown higher and spends more flight time near a 45 degree angle.
Scoober.
Another upside-down variant of the forehand, the scoober (also known as the "Spoon pass" or "Hiawatha") is similar to a hammer, but released away from the body from a backhand stance, instead of over the head from a forehand stance. The scoober travels in a path similar to the hammer, although the initial release is typically more flat than a hammer release. Although it is more difficult to impart power to a scoober than a hammer, a scoober can be an effective short-range (10 to 20 yards/meters) throw and is used in Ultimate for breaking the mark and to throw over defenders in a zone defense.
Thumber.
The Thumber (not to be confused with the "thumber forehand") is a throw that is rarely used in competitive play, compared to the Hammer or standard forehand. It has a flight path that is the mirror-image of the Hammer (arcing high and to the right for a right-handed thrower). It can be useful when the disc needs to drop quickly and fly with an opposite curve to a Hammer in order to avoid defenders.
Table of basic disc throws.
This table represents the fundamental disc throws with classic technique in the foreword form, in fact exist many variations of throws and grips that make the number of pitches quite infinite. 
The "natural path" is the trajectory the disc takes without pre-release tilt.
The "hyzer path" is the trajectory the disc takes when the outside edge of the disc is tilted downward.
The "anhyzer path" is the trajectory the disc takes when the outside edge of the disc is tilted upward.
The "spin" is the rotation of the disc.
Every throw can be done with the right hand or the left hand and this is shown in the "hand" column.
RH=right hand, LH=left hand, R=the path tends to the right of the thrower, L=the path tends to the left of the thrower, 0 means that the path is quite linear.
So R with RH and L with LH are outside-in (OI) paths; R with LH and L with RH are inside-out (IO) paths.
In "spin" column numbers represent the sign of the angular momentum relative to the upside of the disc (+1=positive (counter-clockwise rotation), -1=negative (clockwise rotation)).
Throws may be signed as follows: hand acronym+throw acronym+tilt acronym. For example LHBHIO is an inside out backhand throw pitched with the left hand; RHFH0 is a linear forehand throw pitched with the right hand. To have linear paths the disc must be released with a light opposite tilt than his "natural path".