Equitable estoppel is a legal concept that prevents a person from going back on their word or actions, if it would be unfair or unjust to do so. Essentially, it means that if someone makes a promise or behaves in a way that leads another person to reasonably rely on that promise or behavior, they cannot later change their mind and act in a way that harms the person who relied on them. Equitable estoppel helps ensure fairness and prevent one party from taking advantage of another.