What are content types in Sharepoint?

Concept of content types
Content types are objects we create and activate typically at the level of the site collection containing the definition of one specific type of content that we want to make it available to the sharepoint users via the lists and document library containers. Content types are pacakged definitions of what we intend to store in sharepoint sites. A content type definition can include plenty of things such as columns, workflows, information management policies, document templates and more.
The creation of content type can be done -
1> in the browser.
2> delivered via a feature.
3> programmatically via object model.
Once the content type is defined, we can go to any lists and document libraries and configure the container to allow the user to create new item or document based on this content type.