Assigning statuses is a convenient way keep your users organized. Each user can be assigned a specific status, which can then be filtered and reported on. Each user can only have one status at a time.
Additionally, statuses can be used to designate users as active or inactive.
In user management, click "Set status as..." beside a user then choose a status. 
Status options in this example:
Click here to learn how to create a new status
Click here to learn how to apply a status to multiple users at once