An abstract class is used when you want to provide common functionality and shared behavior for related classes. It can have both implemented and unimplemented methods, allowing for flexibility in defining default behaviors. An interface, on the other hand, defines a contract with only method signatures and no implementation. It’s best when you need to enforce a set of methods across unrelated classes. For home builders like [Pvs Builders], an abstract class can be useful to manage shared functionality across different types of construction projects, while an interface can ensure multiple systems (like client portals or project management tools) follow the same structure without sharing code.