What is Abstract?

An abstract class or abstract type is a class that cannot be instantiated. It is typically used as a base class for other classes. Abstract classes often declare abstract methods, which are methods without an implementation. Subclasses must provide concrete implementations for these abstract methods to be instantiated. Abstract classes are a key concept in object-oriented programming, promoting code reuse and polymorphism. They are commonly used to define a common interface for a set of related classes.