In the real world, when there is a transaction involving a contract between two persons, there is usually a third person that witness the contract being signed by the two persons involved. On the steem blockchain it is a little bit the same. As a witness, I run a server which runs a witness software. Every time there is a transaction going on (post, comment, upvote, transfer) one witness will be signing the transaction and generate a block (a package full of signed transactions, like a folder full of signed and witnessed contracts). Another important aspect is that the witness servers are holding a copy of the actual blockchain, so no witness = no blockchain = no Steemit!
In other cryptos, miners are doing the same thing but their software relies on their CPU power to try resolve a math problem as fast as possible to generate a block. Then when a block is created, all other witnesses stop working and verify the block is valid or contains a fraudulous transaction. But because Steem is a blogging platform, it cannot afford that time that it takes to mine and verify a block. So Steam is using a method called DPoS (Delegated Proof of Stake) instead. The witness is a trusted person so no one needs to verify his/her work. What does trusted means? This means a lot of users (the people in the Steem democracy) are trusting him/her and cast their vote to approve his witness using their stakes (vests or SP) as a weight. -
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Steemworld.org has a more comprehensive list of witnesses, top 100 to be exact. There are more than 100, currently, I think there are over 130 of them.
On Steemworld you can see a variety of stats pertaining to each witness like the amount of votes these witnesses have, to the blocks they missed and you can even vote for each one using your active posting key here!
Unfortunately, https://steemit.com/~witnesses only shows very little stats for witnesses and only 50 of them. Don't worry you are allowed to vote outside of top 50 or top 100 selections here as well!
A major issue Witnesses have with the witness list on Steemit.com is the fact it only shows the top 50 witnesses and doesn't really give any explanation on them. However, Steemit is disabling 'dead'/ inactive witnesses now, this will help active more witnesses gain more attention and work harder for their witness votes.
Healthy competition here is a must, as it will incentivize more witnesses to improve their equipment as they gain more attention.
Witness voting is all about trust, so if you trust a particular witness or individual on Steemit, you have your witness votes cast to mirror their votes. All 30 of your witness votes will reflect or be cast in the exact fashion as the person or 'proxy' you choose. Becareful though, this will reset all your current selections!
@surpassinggoogle, but still a good proxy to use! Im still getting to know 
@underground but he is full of love and I do trust him too! However, I would research his votes and anyone's witness votes before using them as a proxy)I want to share this informative Steemit post by 
And also this great link I just found that is a comprehensive web page on Steemit witnesses!
