Hi Kiran
Deactivate User: Deactivated user means that user is no longer able to login as well he lost their ownership from all data and their license becomes free can assign to other users. In this case license becomes free , we can assign to other user.
Example : If Employee leaving company ,n that case ou will deactivate to user.
Freeze User:: It means that user will not be able to login for perticular period of time unless admin will not activate him again.In this case user lisence will not get free.
Example : when employees goes for long holidays or other reason.