A more thorough explanation:

Definition: Contestatio litis (kon-tes-tay-shee-oh lI-tis) is a Latin term that refers to the final agreement of the parties to a suit on the formula the praetor would issue to the judex. It is also known as litis contestatio.

Example: In Roman law, when both parties were present or represented before the praetor, the plaintiff would state the nature of their claim and ask for an action. If the praetor refused any action, the matter was at an end. However, if the parties agreed upon the issues to be referred, a document framed in identical terms was issued to the judex by the praetor as his authority to act. This ceremonial in which three persons concurred (plaintiff, defendant, praetor) was the litis contestatio.

Explanation: The example illustrates how litis contestatio was the final agreement of the parties to a suit in Roman law. It was a formal agreement that was reached after the parties had presented their claims and the praetor had issued a formula to the judex. The litis contestatio was important because it established the issues to be decided by the judex and provided the judex with the authority to act.