when to create interfaces

I got the thread from MSDN about when to create interfaces.really it will helpful to understand the need of the creating interface. some points from the thread.

• Interfaces are better suited to situations in which your applications require many possibly unrelated object types to provide certain functionality.

• Interfaces are more flexible than base classes because you can define a single implementation that can implement multiple interfaces.

• Interfaces are better in situations in which you do not have to inherit implementation from a base class.

• Interfaces are useful when you cannot use class inheritance. For example, structures cannot inherit from classes, but they can implement interfaces.

MSDN:when to create interfaces