Equitable estoppel is a legal principle that prevents a person from arguing something contrary to a claim they previously made if another party relied on that claim. This principle is often used in situations where one party has acted based on the representations or promises of another, leading to unfair consequences if the first party changes their position. To establish equitable estoppel, three main elements must be present: a clear and definite promise or representation, reliance on that promise by another party, and resulting harm or detriment to that party. This doctrine aims to promote fairness and prevent injustice in legal disputes.