A more thorough explanation:

Definition: Act in pais refers to an act performed outside of court, such as a deed made between two parties during the transfer of land. It is a voluntary deed or action that results from a person's will being exerted on the external world.

Example: A farmer sells his land to a neighbor and they both sign a deed of sale. This is an act in pais because it is a voluntary deed made outside of court.

This example illustrates how an act in pais is a voluntary action that takes place outside of court. It is a deed or action that is performed by the parties involved and is not mandated by the law.