Okay kiddo, have you ever played with a toy where you can press a button and everything goes back to how it was at the beginning? That's kinda what a reset is in a computer.
Sometimes when you're using your computer, things can get messed up or not work the way they should. Maybe the screen froze, or a program isn't responding. When this happens, you can do a reset to make the computer start fresh and hopefully fix the problem.
Resetting a computer is like turning it off and then back on again. And just like when you turn off a toy and turn it back on, everything goes back to how it was at the beginning, a reset clears out any confusion or mistakes and starts the computer fresh.
But be careful, resetting a computer means you lose any work or information that you hadn't saved or backed up beforehand, like taking apart a Lego creation that you worked on but hadn't taken a picture of or saved. So make sure to save your work before resetting!