Go to Setup > CRM > Contact Categories.
Contact Categories allow you to sort your CRM Contacts into various groups to facilitate searching, filtering, reporting and mail merging.
There are three sub-tabs under Contact Categories, allowing you to group the categories under lists 1, 2 and 3. These three lists are independent of each other, i.e. Contact Categories 2 and 3 are not sub-sets of Category 1. Therefore, you can assign multiple categories from any of the three lists to a Contact.
To learn more about using Contact Categories, see Contact Category Use.
To add a Contact Category to setup, see Create Setup Contact Category.