We have covered the basics of what is Observable.create, and other creation functions. Now lets finally dive into operators, which are the focus of this course. We will see how operators are simple pure functions attached to the Observable type.
Jimish, have you watched the previous course on creating Observables? https://egghead.io/courses/rxjs-beyond-the-basics-creating-observables-from-scratch
A subscribe will invoke the execution of the Observable, but a map will not invoke the execution, it simply returns a new Observable. That returned Observable needs to be subscribed in order to execute. In general, we should never put side effects inside a map operator. Side effects must happen only in a subscribe. The map operator is meant simply for basic data transformation.