What Is a Content Type?

Lists and document libraries can store different kinds of content, known as content types. A site manager can create and manage the content types in a site. The content types are then available in that site and in all the
sites under it. The different types of content may have different site columns and/or different settings, such as policies and workflows, associated with them.

Content types can use site columns only for column definitions. This means that to create a content type, you must choose what site columns should be included in that content type.

A simple example of a content type is a list of contacts that stores two types of contacts—an internal contact and an external contact. The Internal Contact content type is used for a contact inside the company—and as such does not need the company property because all internal contacts are from the same company. However, the External Contact content type does require the company property because every contact may be from a different company. Hence, a single list has two different column requirements.