Depending on your needs, you can classify your contacts into various categories.
If you want to create a new category, navigate to: System > Dictionaries > Contacts. Select Categories from the menu on the left, and press the Add button.
Then enter the name of the category, label it with a color, and click Save.
The new category will then be displayed among all the other categories. You can also add subcategories to the newly created category by clicking the Subcategories button.
Then click the Add button and enter the subcategory name. A new screen will be displayed, as in the picture below.