Presenter

A presenter, or host / hostess, is a person who guides or introduces an event, especially on television.
A similar term is master of ceremonies (MC, "emcee", or host). The main use of the term 'presenter' is on television, where the presenter introduces other speakers, and introduces program sections. The role is similar to narrator, who talks over visuals ("voice over") or plays a main role in the program. A presenter does not have to be an expert on the content of the program, but a narrator or commentatior is often an expert. 
Television presenter.
A television presenter is a person who introduces or hosts television programmes. It is common for minor celebrities to do this. There are also many people whose main job is presenting. This is very common with children's television series. One example of this is Mister Rogers.
Some presenters may also be an actor, model, singer, comedian or other profession. Others may be experts on certain things. These include scientists or politicians They work as presenters for a programme about what they are an expert at. For instance, Carl Sagan, an astronomer was the host of ', a television series that dealt understanding the universe. Some television presenters are celebrities who have made their name in one area and use their fame to work in other areas. Examples of this include British comedian Michael Palin who now presents programmes about travel (such as '), and Alan Alda, who has presented "Scientific American Frontiers".
The term is also used in other countries, such as Ireland. In the United States, the term host or MC (Master of Ceremonies) is commonly used.
News presenter.
A news presenter (also called an anchor, news anchor or newscaster) is a person who presents news during a news program. The program can be on television, on the radio or on the Internet. A news presenter, or anchor, puts together the entire program. This may include writing, selecting, and reading stories on the air. The job of an anchor is often more improvised than scripted. This is especially true during breaking news (when events are happening quickly). They have to coordinate other reporters, interviews and behind-the-scenes events as they happen. They must also deal with technical difficulties and keep the broadcast going.
Other presenters.
There are presenters for many types of things. These include: