"That one" typically refers to a specific item, person, or concept that stands out among others in a given context. It is often used in conversation to indicate a particular choice or preference that is easily identifiable to those involved. The phrase can apply to various situations, such as selecting a favorite book, movie, or even a friend in a group. In social settings, "that one" can also denote a memorable experience or a unique characteristic that distinguishes someone or something. For example, in a group of friends, "that one" might refer to the individual known for their humor or a specific event that everyone recalls fondly. This term encapsulates the idea of recognition and shared understanding within a community.