In Gmail it is usually a Google Group or a delegated account; in Outlook and Microsoft 365 it is a mailbox that several users are given access to. The address belongs to the business, not to one person, so it survives holidays and staff changes.
Why it matters
A shared mailbox is the simplest way to run support without buying a helpdesk. The catch is coordination: two people can answer the same email, or each can assume the other did. Small teams handle this with labels or folders (“mine”, “waiting on customer”), a habit of replying from the thread, and one agreed tone so replies sound like one business.
An example
A shop sends every order question to [email protected]. Two people share the inbox: one mornings, one afternoons. Each opens the thread, sees the full history, and replies from the same address.
In ReplyPen: You can connect a shared address like support@ as your mailbox; today that is one mailbox with one voice per account. See how to run support@ from Gmail.