Billing in filmmaking is like giving everyone their own special name tag at a party. In a movie, there are a lot of different actors and people who work behind the scenes to make the movie happen. When the movie is finished, they all want to know how they will be recognized or identified on the screen.
Just like when you go to a party, you want to know where to put your coat and which room to go to, all of the people who work on a movie need to know where their names will appear in the credits.
The people who make the movie decide who gets top billing – which means their name shows up first in the credits – and who gets second billing, and so on. This is important because it tells the audience who is most important in the movie.
For example, if Tom Hanks is in a movie, he might get top billing because he's a big movie star and a lot of people want to see him. But if there's a new actor who is just starting out, they might get a lower billing because they're not as well-known yet.
Billing is important because it tells people who worked on the movie and how important they are to the success of the movie. It's like saying "thank you" to them for the hard work they put in to make the movie great.