An anorak is a type of coat that keeps you warm when it's cold outside. People use the word "anorak" as a slang term to describe someone who is really interested in something specific and spends a lot of time focusing on it, often to the point of being a bit obsessive. It's like when you really like a toy or a game and you want to play with it all the time, or when you have a favorite food and you always want to eat it. When someone is called an anorak, it means they're really passionate about something and can talk about it for a long time. It's not necessarily a bad thing, but sometimes people use the word to make fun of someone who is too focused on one thing and doesn't have many other interests.