Why @Injectable() { ProvideIn: root} in Angular? | What is Dependency Injection in Angular

Why @Injectable() { ProvideIn: root} in Angular? | What is Dependency Injection in Angular Your Queries: angular injector service angular injector get angular dependency injection angular injector create angular injector example How to inject service to angular constant? Where to give gluteal IM injection? How to create angular application using angular CLI? What are the types of injections? why @Injectable() in angular