I have a site like "example.com".
Questions 1: I can access to my site through "example.com" and www.example.com in web browser. Both non www and www version redirects to example.com. So, is it necessary to add my both version of domain in webmaster tool or I should only add non www version site in webmaster as I can access to my website through www/non www version.
Question 2: When/why do I need to set preferred domain in webmaster tools.
Questions 3: Is it necessary to set 301 redirect, if I set my preferred domain name in webmaster tool.
As I am a non technical guy, I need your valuable feedback to improve my knowledge.