Question

OOP interfaces.

Answer 1

1. An Interface totally abstracts away the implementation knowledge from the client.
2. It allows us to change their behavior dynamically. This means how it will act depends on dynamic specialization (or substitution).
3. It prevents the client from being broken if the developer made some changes
   to implementation or added new specialization/implementation.
4. It gives an open way to extend an implementation.

Programming language (C#, java )

These languages do not support multiple inheritance from classes, however, they do support multiple inheritance from interfaces; this is yet another advantage of an interface.