I never "dove" into a programming language before, and never developed any in my entire life. And I want to start a project while I'm still in High School. So I took interest in Back End Development. There are a lot of concepts that is in field and doing some research, there's hardly anything that helps me.
So, what key concepts do I need to know about Back-End development before I start?
What is the book and online resource that I can learn Back-End in general and programming in Python?
You said you have no development experience so even though you are interested in back-end I'd suggest gaining a working knowledge of the front-end first. I'm a back-end developer now but started with front-end and am glad I did because even on a dev team with dedicated front-end developers I use html, css and javascript ALL THE TIME.
If you want a simple answer go to codecademy.com and do the html/css course, then javascript, then you can dig in to the php course and decide if you want to stick with that or move on to something else like C# or Java.
Here's a good place to find free books - http://resrc.io/
Pyramid is my favorite Python web backend framework. http://docs.pylonsproject.org/projects/pyramid/en/latest/index.html
I'd learn PHP, and Ruby for backend. But you will want to work on front end development too. HTML and CSS will be all you need to try to work with some front end for lets say a website as your resume' for employers.