Okay kiddo, imagine you want to learn how to count to 10, but your mom and dad can't teach you. So you find someone else to teach you instead. But that person is not a teacher at a school, they just say they are. That means they haven't gone to a special school to learn how to teach, and no one else checks to make sure they know what they're talking about.
Well, some colleges are like that. They say they can teach you things and they give you a piece of paper at the end saying you learned those things. But no one else has checked to make sure that the things they taught you are actually worth knowing. So while you might feel like you learned something, that piece of paper they gave you might not be worth anything to other people. It might not help you get a good job or get into other schools. That's what it means when a college is "unaccredited."
Now, there are good reasons for a college to not be accredited. Maybe they are brand new and couldn't get accredited yet. Or maybe they teach really specific things that aren't normally taught at other schools, so they don't fit in to the usual accreditation standards. But other times, it's because the school isn't doing a good job and can't meet the standards that other schools have to meet to become accredited.
So if you're looking to go to college, it's very important to make sure the school you pick is accredited! That way you can be sure that the things you'll learn are valuable and that the degree you earn is worth something. Otherwise, it might be like learning to count from that person who didn't really know how to teach you after all.