Flea Markets are a giant "yard sale" but at a place meant for this type of event.
Flea Market

A flea market

People gather from all over the area to come and shop. People go from lot to lot and browse through all the stuff you want to get rid of. At a flea market anything can be found like Pokemon cards, Silly Bandz, or pets! People never know what can be found at a flea market. Things that do not sell are taken back to the owner's house and they usually will have another flea market in the future. You can buy toys and many other stuff too! Most of the stuff at Flea Markets are cheap. Flea Markets have very random things to Games, Furniture, and many other great things are found at flea markets.

In the Animal Crossings Series, once a month on a Saturday or Sunday, a flea market is held. The villagers will either go to the player's house or they go to the villager's house. The villagers will choose three items they will sell to you. They will look around your home and choose three items they like. Players will choose the price and determine if they will sell that particular item or not. If you have money you can buy something at the villagers house but they might not give it to you. For example, the player will ask if they can have a cabana dresser from Kiki and if Kiki says yes the player has to buy it for a current amount of money if they say no you do not get the current item that you picked out.