What is a seller's concession?

It works like this: suppose you agree on the price of the house at, say, $200,000. You then ask the seller for a 3% seller concession. What this means is that you add 3% to the price of the house. That's right, you're now going to pay $206,000 for that house -- but the seller is going to give you that $6,000 back when the sale takes place. You're going to use that money to cover all of your closing costs.

It is also a term that can be used for a selling venue at a fairgrounds, amusement park, etc. (concession stand)