"Can't" is a contraction of the words "cannot," which indicates an inability or lack of permission to do something. It is often used in everyday language to express limitations, whether physical, mental, or situational. For example, someone might say, "I can't swim," meaning they do not have the ability to swim. In addition to personal limitations, "can't" can also refer to rules or restrictions. For instance, a sign that says "You can't park here" indicates that parking is not allowed in that area. This usage helps communicate boundaries and expectations in various contexts, such as in schools, workplaces, and public spaces.