The most consolidated post explains and answers the questions and raises new questions,

**The clearest guide to understand what are "Witnesses". They are essential to Steem. Without them, Steem can't exist. Support them and they'll support you. This is a core principle that most Steemians haven’t thought much about and one this post hopes to solve**

Here is the source for everyone to know more about the witnesses and the nodes, why witnesses and how does one witness and how a witness is created, how are they rewarded. 

Original post: 
https://steemit.com/witness/@teamsteem/what-are-steem-witnesses-and-why-you-should-support-them

I hope everyone commenting here needs to go through the post for better understanding on the functionality. I'm no different than you all.