What is the Dependency Inversion Principle, and how does it differ from Dependency Injection?

Dependency Inversion is a design PRINCIPLE stating that high-level modules shouldn't depend on low-level modules directly — both should depend on abstractions (interfaces). Dependency Injection is a PATTERN/TECHNIQUE for actually supplying those dependencies (typically via constructor) from the outside rather than a class creating them itself; using DI doesn't automatically guarantee DIP — you can inject a concrete class directly instead of an interface, which still violates the principle even though the dependency is technically 'injected.'