Okay, kiddo! So, imagine you have a big Lego set that you need to build. Now, let's say that you have all the pieces in a box, but they are not organized at all. Some pieces are at the bottom, some are at the top, and others in the middle. This mess of tiny pieces is what we call "fragmentation."
Now, let's move on to the computer stuff. When you save a file on your computer, the computer stores it in small pieces (called clusters) on the hard drive. If the file is bigger than a cluster, the computer will break it into smaller pieces to store it separately across the hard drive. Just like with the Lego set, these pieces can end up scattered all over the place, in a messy way.
When your computer needs to access that file, it needs to go look for those different pieces on the hard drive, and that can take longer because it has to keep moving back and forth to find all the pieces. This is what we call "file fragmentation," and it can slow down your computer.
Now, there are tools called "defragmenters" that can help organize those pieces of the file so it's easier for the computer to find them. It's like cleaning up your Lego set and putting all the pieces together so it's easier to build. And just like with your Lego set, it's important to keep your computer's files organized, so it runs faster and smoother.