Tentative describes something not fixed or certain yet — a plan, an idea, or an answer that might still change. A tentative date for a meeting means 'this is the date for now, but it could move'. Tentative can also describe a person's manner — speaking or acting in a careful, unsure, not-fully-confident way, like someone testing the water before they commit — a tentative smile, a tentative step forward. In both uses, the feeling is the same: not fully decided, ready to change if needed.