Welcome to another Steemit Q&A, Let get started:

Q: What is voting power

A: Voting power is like an "energy bar" in a computer game that goes down a little bit every time you vote. The lower power you have, the less your vote worth.

You get started with 100% full power. Each time you vote, your power goes down a little.

at the end of the day, the network recharges it by 20% 

For example: You start with 100% voting power. Within a day, you up-vote 20 posts and it goes down to 50%. After the end of the day, Steemit will add 20% Voting power for your account so tomorrow you will start at 70% voting power.if you don't vote tomorrow then the next day after tomorrow, you'll have 90% voting power.

You start with 100% voting power. But if you don't use it, then the 20% power added to your account per day by Steemit will have no affect at all (100% is already Max) 

Q:How much my Up-vote worth?

A: The best way to know is just upvote for someone to see how much the money increase.

The more Steem Power (SP) you have in your wallet, the more your vote worth.

The math to calculate should be: (SP)/[(number of vote) + (x)]

i think x = 10 or 20 or i'm not sure. the Dev probably make some changes ... just up-vote someone and see how much their money increase.

http://www.steemdollar.com/dollar_per_vote.php

this tool above can help calculate how much your vote worth but keep in mind, it still testing and can be wrong.

Q: What is voting strength?

A: This Voting strength only effect you if you have over 500 Steem power (SP) in your wallet.

After you have over 500(SP) in your wallet, you will see a vote slider appear when you vote, this is call Voting strength.

The more voting strength you use, the more voting power you will lose but your vote will worth more.

And the opposite is also true. Less voting strength = less voting power lose = your up-vote worth less.

Let summary these whole power, strength things a little so you can understand this easier:

There are three things that will effect your vote

- Voting Power: More up-vote = less Voting power = your upvote worth less (start at 100%, recharge 20% per day)

- Amount of Stem power (SP) in your wallet: More SP = your upvote worth more

- Voting strength (required 500(SP) in your wallet): More Voting strength = More voting power spend.