A flea market is like a big yard sale where lots of different people come to sell their old things like clothes, toys, books, and other stuff. It's called a flea market because sometimes there are fleas on the old things people are selling, but don't worry because most people clean their stuff before selling it.
When you go to a flea market, you get to walk around and look at all the different things for sale. Some sellers have tables or booths where they display their items, and others may spread their things out on blankets on the ground. You can find all kinds of things at a flea market, from old records and comic books to antiques and vintage clothing.
Sometimes you can buy things at a really good price, because the sellers want to get rid of their old things and make some money. It's a fun place to visit and you never know what treasures you might find!