Dialing an extension is a way to connect to a specific person or department within a company or organization. It is typically used when calling a landline phone number, and requires the caller to enter the extension number after dialing the main phone number.
Extension numbers are usually 3-5 digits long, and are assigned to individual employees or departments. Dialing an extension can be useful for reaching the right person quickly and efficiently, without having to go through a receptionist or operator.