Answer 1

https://www.sololearn.com/discuss/339710/?ref=app
https://www.sololearn.com/discuss/625628/?ref=app

Answer 2

In software engineerig, the terms front end and back end refers to the separation of concerns between the presentation layer(front end), and the data access layer (back end) of a piece of software.
source https://en.wikipedia.org/wiki/Front_and_back_ends

Answer 3

it will really be great if you learn both.

Answer 4

Are you asking what you should learn? If so it is up to you. Whether you should learn front-end or back-end programming. If so can't really help. It depends on whether you want to work with data management (back-end) or UI front-end.