The disclosure made to participants after research procedures are completed, in which the researcher explains the purpose of the research, is called

I believe the answer is: Debriefing

During the process of the research, the researchers often forced to keep the true purpose of the research hidden in order to prevent data skewing from the participants. This might create some sort of distress or discomfort for the participants.

During the debriefing, the researchers are ethically required to reveal all of this information to the participants in order to resolve the discomfort that may occurred.