Alright kiddo, you know how sometimes when you're building with blocks, you realize that the tower you made isn't very strong or stable? So you take some blocks apart and build the tower again in a better way, so that it's stronger and stays upright.
Well, when grown-ups write big computer programs, they sometimes realize that the code they wrote isn't very good or efficient. That's when they "refactor" the code. They go in and change the code to make it better and more efficient, just like how you took apart your tower of blocks and rebuilt it stronger.
This helps make sure that the program runs smoother and faster, and that any bugs or issues with the original code are fixed. Refactoring is like giving the program a tune-up, making sure everything is running at its best.