Central casting is like a movie factory where they make lots of movies. Think of it like a big toy box full of different kinds of toys. Instead of toys, Central casting has lots of people who all look different and can act in different ways.
When the people who make movies need some "actors" to be in their movie, they go to Central casting and look through their toy box of people. They pick the ones they want and then use them in the movie.
Sometimes, these people who work at Central casting might have to make some of the actors look different, like putting on makeup or changing their hair, so they can look like the character in the movie.
So, in summary, Central Casting is a place where they have a lot of people who are ready to act in movies, and they help people who make movies find the actors they need. Like a big toy box with different-looking people who can act!