Using Content Types and Columns

A content type is simply a content item plus its metadata fields. We are combining the discussion of columns and content types because the way you assign metadata to a content item is by adding a column to the list and then populating that column for that data item.

Therefore, you can allow the library to manage content types. This means that you can allow multiple document templates in your library because different templates include a unique document (such as a Microsoft Office Word or Excel document) plus columns of metadata to populate. By doing this, users can then click on the New button in the library and select the document template they want to use when creating a new document. By default, each document library only has one template. If you need more than one document template in your site, select the Yes option in the Content Types area and choose the content types you wish to associate with your document library.

For example, you can have a Word document with one set of columns describing the Word documents, another set of columns describing Excel documents, and a third set of columns describing PowerPoint files-all within the same document library. Content types need not use the same columns, but they also are not restricted to using only unique columns. Different content types can both share columns with other content types as well as have their own unique columns. This flexible feature allows you to describe documents of different types in similar and/or different ways within the same document library.

Note 

Consult your System Administrator if you need more information about content types, how they work, and how they are created.