A television presenter is a British term (American:host) for a person who introduces or hosts television programmes.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.
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.Some are celebrities who have made their name in one area,then leverage their fame to get involved in other areas.Examples of this latter group include British comedian Michael Palin who now presents programmes about travel (such as Around the World in 80 Days),and Alan Alda,who has presented Scientific American Frontiers for over a decade.
The term is also used in other countries,such as Ireland.In the USA,such a person is typically called a host or an emcee (perhaps from MC:Master of Ceremonies).
A news presenter is the host of a newscast.