Short Answer:

Classical Dependency Injection/Inversion of Control uses a class interfaces as placeholder for dependant functionality. This interface is implemented by a class.

Instead of Interface/ClassImplementation many dependencies can be easier implemented with a delegate function.

You find an example for both in c# at ioc-factory-pros-and-contras-for-interface-versus-delegates.

Short Answer:

Classical Dependency Injection/Inversion of Control uses a class interfaces as placeholder for dependant functionality. This interface is implemented by a class.

Instead of Interface/ClassImplementation many dependencies can be easier implemented with a delegate function.

You find an example for both in c# at ioc-factory-pros-and-contras-for-interface-versus-delegates.