The term "mailing" has several meanings, depending on its context.
1) In a general sense, mailing refers to sending something through the postal service or by courier. For example, one might say that they sent an email or a letter via mailing.
2) Mailing can also refer to the process of delivering advertisements through the mail system. This is often used in marketing and direct mail campaigns where businesses send out promotional materials such as flyers, brochures, or catalogues to potential customers through the postal service.
3) In a more technical sense, mailing can refer to an email newsletter or other types of electronic communications that are sent to a group of people at once. This is often used in marketing and communication strategies where businesses send out regular updates or information to their subscribers through email.