A presenter host or hostess is a person or organization responsible for the running of a public event. A museum or university, for example, may be the presenter or host of an exhibit. In films, a presenter (but not a host) is a usually a well-known executive producer credited with introducing a film or filmmaker to a larger audience. For example: "Presented by Cecil B. DeMille".
In the broadcast media, a presenter is the person who hosts, narrates, or otherwise takes the main role in narrating or hosting a radio program or a television program. The phrases "television presenter" or "radio presenter" are never used in American English, and rarely in Canada.
A person who hosts other kinds of public entertainments may also be called a master of ceremonies (often abbreviated "M.C." or "emcee").
A television presenter is a person who introduces or hosts television programmes, including factual documentaries, live events, and sports. Nowadays, it is common for minor celebrities in other fields to take on this role, but there are also a number of people who have made their name solely within the field of presenting, particularly within children's television series to become a television personality.
Some presenters may double as an actor, model, singer, comedian, etc. Others may be subject matter experts, such as scientists or politicians, serving as presenters for a programme about their field of expertise (for example, Sir David Attenborough). Some are celebrities who have made their name in one area, and then move on to get involved in other areas. Examples of this latter group include the British comedian Michael Palin who now presents programmes about travel (such as Around the World in 80 Days), and Alan Alda, who has been the host of the Scientific American Frontiers TV program for about a decade.