Okay kiddo, you know how you look in the mirror and you can see your reflection? Well, in programming, a mirror is kind of like a special mirror that reflects websites or software.
Let's say you have a website or a big software program, and lots of people want to use it all at the same time, but it's getting too slow and it's hard for everyone to use it at once. That's when we use a mirror!
A mirror is basically a copy of the website or software that's kept on another server (a server is like a big computer that stores information). When you use a mirror, instead of all the people using the main website or software program, some of them can use the mirror instead.
This way, the people using the main website or software program aren't all trying to do things at the same time, which makes it faster and easier to use. And because the mirror is just a copy, everything works the same way as the main website or software program, it's just stored in a different place.
So, in summary, a mirror is a copy of a website or software program that we can use to make things faster and easier to use for lots of people at the same time!