Okay little one, have you ever heard of dumping? It means getting rid of something you no longer want or need. Dump months are the times of the year when movie studios release movies that they aren't very excited about and don't think will do well in the box office.
Think of it like cleaning out your toy box. You might throw out old toys that you don't play with anymore, and the movie studios throw out movies they don't think people will want to see.
The dump months usually happen when people are busy doing other things, like going back to school in September or celebrating the holidays in December. During these times, movie goers are less likely to go to the theaters, so the studios release movies that they don't care as much about during these months.
But just because a movie is released during a dump month doesn't mean it's bad! Sometimes there are hidden gems that don't get noticed because they were released during a less busy time. So next time you see a movie that was released in a dump month, don't immediately think it's bad. You might just find a new favorite!