Interfaces in TypeScript provide a way for you to define the structure, or contract, that objects and classes must follow. Unlike classes, interfaces do not provide any implementation details. Instead, they describe what properties and methods an object should have, ensuring consistency and type safety across your codebase. This is especially useful when you want multiple classes to share the same structure or behavior without enforcing inheritance.

In the code above, the Printable interface defines a single method, print. The Document class implements this interface by providing its own version of the print method. When a class implements an interface, TypeScript enforces that the class must provide concrete implementations for all the members defined in the interface. However, the interface itself does not dictate how these methods are implemented—only that they exist. This means interfaces enforce structure without providing any actual code, allowing different classes to implement the same interface in their own unique ways.