What is an "assignment fee"?

[Travis Avenarius]

Hello, I am new to investing and I am doing some studying but I keep hearing about an assignment fee.....what is ts, and how much is it? 

Im guessing.......its when you put into your contract when buying from a seller, when the contract has your name, and or assigns. that when someone else comes to the closing table on your behalf (the buyer, or the attorney) that there must be an assignment fee paid to that party?

Thanks! I hope this helps other people too!