using BETA in stock screening ....

So I understand the basics of Beta, and it's use in comparing a Stock with " X " Beta to a benchmark, such as the S&P 500

What I don't quite understand though is .... What is a Stock with a " Extreme " Beta telling me exactly ?

For example :

Lets take 2 different stocks.... one has a +3 Beta and the other stock has a -2 Beta
how can I look to trade stocks that have Betas in the upper and lower " Extremes "
What exactly is this telling me ?


Thanks as always for any help and insight