When you create a new reference, that reference is assigned the default reference type. If you want to add a different type of reference, click the Reference Type list at the top of the Reference window, and select the reference type that you need.
Normally, you should select the reference type before entering information in the reference. However, you can change the reference type at any time, and the information you have entered is retained and transferred to the corresponding field for the new reference type.
In addition to determining how the reference is formatted in the bibliography, the reference type determines which fields appear in the Reference window. For example, a Journal Article reference would have fields for Journal, Volume, and Issue, whereas a Book would have fields for Editor and Publisher.
Fields can be removed, added, or renamed. You can also rename reference types. See Customizing Reference Types for more information.