Okay kiddo, so when people make movies, they need to have a plan for how much money they can spend on making it. They call this plan a budget.
Now, making a movie costs a lot of money because there are so many things that need to be paid for. They need to pay the actors who are in the movie, they need to pay for the cameras and equipment used to film it, they need to pay for the people who help make the sets and props, and they need to pay for lots of other things too.
So, before they start making the movie, they need to figure out how much money they can spend on each part of the movie-making process. They have to decide what scenes they want to film, how many people they need to hire, and how long it will take to film. All of these things are written down on a piece of paper called a budget plan.
When they know how much money they can spend on making the movie, they make sure to stick to the budget plan so they don't run out of money before the movie is finished. They keep track of all the money they spend while making the movie to make sure they're not overspending.
Sometimes things don't go as planned and they need more money than they thought they would. When this happens, they might have to cut some scenes from the movie or find more money to keep going.
So, film budgeting is like making a plan for how much money you can spend on a movie and then keeping track of all the things you buy to make sure you don't run out of money.