defined in the Glossary in the Getting Started section, a A recipient is any contact in a List.
There are three recipient statuses managed at the List level:
A recipient will only receive messages from you if the status is that of a "Subscribed", and, therefore, should never be confused for a subscriber unless assigned that status.
Recipients and custom fields
Each recipient has 39 custom recipient fields available and freely customizable.
Custom fields are useful to (e,g. Dear and the customer's first name) or to segment your subscribers using Filters.