What does an abstract class in C# refer to?

In C#, an abstract class is a class that cannot be instantiated, it can only be inherited. Abstract classes usually include abstract methods (methods without implementation), which must be implemented by subclasses in order to be instantiated. Abstract classes can also contain non-abstract methods and properties, which subclasses can optionally override.

Abstract classes are typically used to define generic methods or properties, allowing subclasses to customize them according to their own needs. By utilizing abstract classes, a template method design pattern can be implemented to reduce the writing of repetitive code.