Rocket-propelled grenade

A rocket-propelled grenade or an RPG is the name for any kind of weapon, held on the shoulder that fires rockets that have an explosive warhead. These warheads are attached to a rocket motor and the rocket has fins which help it to fly straight. Some types of RPG are reloadable, while others are used only once and then thrown away. RPGs, with the exception of self-contained versions, are muzzleloaders, loaded from the front end. 
RPGs with High explosive anti-tank warheads are very effective against armored vehicles such as armored personnel carriers (APCs). They can also be used against tanks, as long as the shooter targets a weak part of the tank, such as the tracks or the top door of the turret. 
In general, the front armour on a tank is too thick to be penetrated by an RPG warhead. In some cases, teams attacking tanks with RPGs will have multiple RPG users fire at the same tank, which may penetrate the armour. Insurgents have sometimes successfully used RPGs to shoot at helicopters.