I'm gonna answer this a bit simpler for you than Zy did. Just cause I think it helps to hear things in a different way for some people. Zy's post was so money, but I remember back when I was trying to figure out pot odds and shit for the first time and saying, "huh," even when it was explained thoroughly.
1) Yes. If you're pot odds are 5:1 and you are a 3:1 favorite to win the hand, call. If the pot odds are 3:1 and the chance of you hitting the best hand are 5:1, you fold. (ignoring implied odds for the example).
2) You can odds to %s simply. 9:1 odds say that you are going to miss 9 times for every 1 time you hit, in ten trials. So, putting it simply, you will hit 1 out of 10 times. 1/10 = 10%.
My suggestion is learn how to count your outs properly. Okay, I'm behind here, but I have 8 outs to improve, etc. For the time being, find a good odds chart like the one in SSHE.
It shows you that if you have X outs, you need X:X pot odds to breakeven. So then you'll know your odds of hitting w/o timing out!
Then just count the odds the pot is laying you (i.e. 8 bets in, 1 more to call). After a while, you won't need the chart anymore. The most frequent draws will be cemented in your brain.