Beta and Correlation coefficient

Correlation coefficient can range from -1.00 to +1.00, and is a measure of the predictability of the price of a stock, when given the movement in the price of the second stock. The further the value is from zero, the higher the predictability (correlation).
For example:
A value of +1.00 would mean that the prices of two stocks are in perfect positive correlation - a rise in one stock price would guarantee a rise in the other.
A value of -1.00 would mean perfect negative correlation - a rise on one, would guarantee a fall in the other.
A value of 0 means no correlation - the two stocks would seem to act completely independant of each other.

Beta measures the volatility/"riskiness" of a stock. It is how much the price of a stock reacts, compared to the market.
This value can theoretically take on any value (even negative), but will usually be between 0 and 100.
A value of 0 means the percentage change in value will be zero, when compared to the index. Cash has a beta of zero, as its value won't change, regardless of the index.
A value of 1 means the percentage change in value will be equal to (1x) that of the index.
Low-risk stocks have a value between 0 and 1. High-risk stocks have a value above 1.
A value of 100 would mean the expected change is 100x that of the index. From this, you can see why extremely high values are not plausible (e.g. a small drop in the index would cause the share price to plummet to zero).