In everyday terminology, the term quid pro quo can best be defined by the phrase "I’ll scratch your back, if you scratch mine." In other words, you’ll give something (e.g. a good or service) to someone else in exchange for that person giving you something (e.g. a good or service). So, quid pro quo refers to a mutual agreement between two parties where each party provides a good or service in return for a good or service.

In the context of law, quid pro quo essentially means "something for something." It occurs most often in contract law. For example, a binding contract must involve quid pro quo, also called legal consideration. Consideration is generally defined as the exchange of something of value for something else of value. And if the exchange between the two parties appears too one-sided, a court could potentially void the contract by law.

Quid pro quo can also refer to legal or illegal transactions. For example, legal transactions occur all the time where one party sells a product or service to another party for something of value (e.g. money). This mutual exchange is a legal quid pro quo. On the other hand, quid pro quo can refer to an illegal transaction such as blackmail. For example, blackmail occurs if one person threatens to refrain from hurting another person in exchange for something valuable. Let’s take a look at a legal and illegal quid pro quo transaction to clarify the term.

Assume Bill offers to paint his neighbor’s house for $1,000. Bill’s neighbor, Mel, agrees to Bill’s offer. Bill then paints Mel’s house and Mel pays Bill $1,000.

Here, quid pro quo occurred through contract law in the form of consideration. Bill offered his services to paint Mel’s house in exchange for Mel’s $1,000. So, services in the form of painting a house were given by Bill, and Mel gave Bill $1,000. In other words, something of value was given for something else of value.

Assume Bill works at a car dealership and John is running for local state election.

Bill can legally support John for election with campaign money within the confines of the law. And John can legally work to pass laws favorable for Bill. At this point, there is no quid pro quo. In other words, Bill has simply donated money as a gift to John without expecting or receiving anything in return.

However, Bill cannot donate to John’s election with the clear and sole intention that John must repay Bill a favor for Bill’s donation. This is a form of bribery and undermines the political process. It is also a form of quid pro quo – i.e. something (Bill’s money) for something (John’s action to pass favorable laws for Bill). Now, do situations like this happen in the political process? Sure they do. Are they illegal? It depends on the facts. But a person cannot donate money to candidate as a form of bribery.

So, as you can see, the term quid pro quo means "something for something," and can be referred to in a positive or negative connotation depending on the situation.