Okay kiddo, so have you ever played with a toy that has buttons that you push to make it do different things? Imagine if that toy could remember every time you pushed a button and what happened when you did. That's kind of like what rundata is!
Rundata is just a fancy name for a bunch of information that is collected when you do something on your computer or phone. For example, every time you click on a link on the internet or type something into a search bar, rundata is created to remember what you did and when you did it.
Now, imagine all of these little bits of information stored in a special place. This is almost like a big memory box for your computer or phone. If you ever need to know what you did before, you can look back at the rundata to see what happened.
So, overall, rundata is just a way for your computer or phone to remember what you did and when. Pretty neat, huh?