So, what is a service?
A Service is just a function for the business layer of the application, it’s just a simple function. It acts as a constructor function and is invoked once at runtime with new, much like you would with plain JavaScript (Angular is just calling a new instance under the hood for us).
Think about it being just a constructor method, you can add public methods to it and that’s pretty much it. It’s a simple API, don’t overthink it.