Using Contact types you can categorize your contacts. The types created here are found in Marketing - Contacts.

Tick a Contact Type for that contact to be grouped. This is also possible in bulk, and lets you perform a search that finds certain types of contacts. A contact can have several types assigned to them, and therefore belong to several categories. For example, find all your sponsors or all your employees in one go. You can then email, send tickets, export to an external file or edit those groups.