1. What

Interface and Abstract class are used to achieve the oops feature polymorphism and abstraction.

2. Difference

Features	Abstract class	Interface
Purpose	Provides a base class with shared logic	Defines a contract (what must be implemented)
Methods	Can have abstract (no body) and concrete (with body) methods	Only method signatures (no body)
Properties	Can define properties (variables)	Cannot have regular properties
Inheritance	Single inheritance only	A class can implement multiple interfaces
Use Case	when you need to share code across related classes with comman structure	when you want to enforce comman structure across unrelated classes
Access Modifiers	Can use public, protected, or private	Methods are always public
Constructor	Can have constructors	Cannot have constructors