PEG is Price/Earnings to Growth. It is calculated as Price/Earnings/Annual EPS Growth. It represents how good a stock is to buy, factoring in growth of earnings, which P/E does not. Obviously when PEG is lower, a stock is more undervalued, which means that it is a better buy, and more likely to go up.
PEG is Price to Earnings Growth. I've forgotten how it's calculated, I just remember that a PEG ratio of 1-2 is attractive by Graham & Dodd standards.
What is value investing? What are the key principles of value investing?