Service Contracts Categories

Hi,

Can someone care to explain the Functionality and purpose of Contract categories. (I understand there are limitation on certain categories where additional categories cannot be created/modified)

How does the structure of Category form allows a flexible functionality.

How does a contract category affect the contracts that is created.

Is there is any workflow assigned behind these categories.

Classes:

I see there is a Class field in the category setup form with limited number of values to select.

What are these classes and where are they setup or where the setup can be seen.

I understand that Service Agreement is used for - Warr, Ext.Warr, Usage and Subscription. What is the purpose of other classes and where are they used - Corporate, Lease Contract, License agreement, Master Agreement, Project Contract, Rights Contract.