A more thorough explanation:

The term “bargain” has two legal meanings:

In contract law, a bargain is a voluntary agreement between two parties in exchange for something of value. This can be money, goods, services, or a promise to do something. For example, if someone agrees to clean a bedroom in exchange for $50, that is a bargain. However, not all bargains are contracts. If an agreement involves an illegal transaction or the consideration is insufficient or illegal, the bargain does not amount to a contract.

In criminal law, bargain is used to describe several prosecutorial practices such as plea bargaining or fact bargaining.

Plea bargaining is an agreement between a prosecutor and a criminal defendant whereby the defendant pleads guilty in exchange for a more lenient sentence or a dismissal of other charges. For example, if someone is charged with robbery, they may agree to plead guilty to a lesser charge of theft in exchange for a shorter prison sentence.

Fact bargaining refers to an agreement between a prosecutor and a defendant ascertaining some facts as true in exchange for the prosecutor’s not introducing other facts that would be detrimental to the defendant. For example, if someone is charged with assault, they may agree to admit to hitting the victim in exchange for the prosecutor not introducing evidence that they had a history of violence.

These examples illustrate how a bargain can be used in both contract law and criminal law to reach an agreement between two parties.