The phrasal expression "quid pro quo" comes from Latin and is often used in English conversation. In general, "quid pro quo" means an exchange of some services or goods, each of the same value. In everyday life the term is usually used to express "a favor for a favor" meaning.

"I want something, you want something. You give me what I want, I'll give you what you want. Quid pro quo."

More Info: www.wikipedia.org