ASP.NET State Management

Definition-:

State Management: By name it means managing or preserving state of a control, web page or data.

Whenever we work on a page in asp.net have we ever thought how controls are able to get there state back after a post back. In real all the controls are stateless means when ever there is a postback state is lost. Then how are they able to get there state back after a postback???
This is all because of state management technique that asp.net provides for all the controls, web pages or data.

Now the question comes. How?
How are state management techniques used? Is it used on server side or client side? How many types of state management techniques are there?