What is ASP.NET OutputCache Directive- Directives And how to use

What is ASP.NET OutputCache Directive- Directives And how to use:

The OutputCache Directive:
The OutputCache directive controls the output caching policies of a web page or a user control.

The basic syntax of OutputCache directive is:

<%@ OutputCache Duration="15" VaryByParam="None"  %>

Some Others Are 

IMPORT DIRECTIVE

MASTER DIRECTIVE

MASTERTYPE DIRECTIVE

OUTPUTCACHE DIRECTIVE

PAGE DIRECTIVE

PREVIOUSPAGETYPE DIRECTIVE

REFERENCE DIRECTIVE

REGISTER DIRECTIVE