Bilateral Contract

A bilateral contract consists of a deal between two parties (hence the "bi" part if it, like bicycle or bifocal or any other "bi" that you can think of, because we certainly can't think of any). Under the deal, one side promises to do something and the other side promises to do something in return.

The agreed exchange could be as basic as "I give you this thing and you give me some money." A bilateral contract is fundamentally a fancy term for what everyone thinks of as a standard vanilla contract.