The witnesses run code that sets the rules for how the blockchain works. If witnesses choose to run a new set of code (a fork), then it can change the everyday operations of how you are allowed to interact with your steem account. They can change the number of days you can power down, add more steem to the reward pool, alter the price of steem, even freeze your account, and more!
Think of it like electing leaders to run your government. Except, not all votes for witnesses are equal. People with the most SP have the most influence in deciding who gets to become our top 20 witnesses. Think of 1 steem as representing 1 vote.
We need every person with a stake in Steem to cast their votes right now for our original top 20 witnesses.
Please read some more posts about the witnesses who most need your support. I know it can be hard to choose 30 votes, but over time you will learn more about a few that you most trust. You can also choose a favorite Steemian you trust, and proxy all of your witness votes to them to handle for you.
RE: What is Witness Vote? Tell Me More About It...