For data or logic that is not associated with a specific view, and that you want to share across components, you create a service class. A service class definition is immediately preceded by the @Injectable decorator. The decorator provides the metadata that allows your service to be injected into client components as a dependency.
Dependency injection (or DI) lets you keep your component classes lean and efficient. They don’t fetch data from the server, validate user input, or log directly to the console; they delegate such tasks to services.
