RxJS consists of some core concepts that are important for you to understand early on. Those are:

• Observable: This is a class representing a stream of data.
• Observer: This is a class able to emit data.
• Producer: This is what internally produces data, which the Observer ultimately emits.
• Operator: This is a method on an Observable, which allows us to manipulate the stream itself or the data it emits.
• Stream: This is synonymous with an instance of an Observable. The reason for it being called a stream is that you should think of the data as continuous and not really having an end, unless you explicitly define an end.