"Mr." is a common title used before a man's last name or full name. It is a sign of respect and is often used in formal situations. For example, you might say "Mr. Smith" when addressing a man named John Smith. This title is widely recognized in many cultures and is used in both professional and social contexts. In addition to its use as a title, "Mr." can also represent a certain level of formality. It distinguishes adult men from boys, who are often referred to as "Master." In business settings, using "Mr." can convey professionalism, making it important in interactions with colleagues or clients, such as Mr. Johnson in a meeting.