What common features do a regular class and an abstract class have, and how are they similar?

Go does not have classes in the traditional sense like in other object-oriented languages, but you can draw an analogy with types and interfaces.

In the context of regular classes and abstract classes in general object-oriented programming, they share common features:

• Both can contain fields (state) and methods (behavior).
• Both serve to encapsulate logic and data.
• Both can be used as a base for creating new types through inheritance or composition.

Differences:

• An abstract class cannot be instantiated directly and often contains abstract methods (without implementation), which must be implemented in subclasses.
• A regular class can be created directly and usually contains a complete implementation.

In Go, to achieve similar functionality, interfaces (to define behavior) and structures with methods are used. Abstract classes are replaced by interfaces, and regular classes are replaced by structures with methods.