Well, I want to include.com in your list also because we use it mostly. So .org, .net and .com suffixes are top level domains.
A domain name is the address where a users can access your website.
Experts categorize domains as per purpose.
If you want to open a website for networking purpose then you will use .net platform.
Ex- slideshare.net , www.php.net
If you want to open a website just for not for profit (non-profit) then you will use .org platform.
If you want to do activities for commercial purpose(business etc) then use .com platform.
Ex- www.google.com, www.answeree.com