A stock's beta sounds like a complicated concept but it has a fairly straightforward explanation. If a stock's beta is one, it tends to move in step with the overall market. A stock with a beta less than one is less correlated with the market and higher than one moves in line with the market but with more exacerbated, volatile moves.
So, depending on if you want to follow the market or not, beta provides a tool to manage that. Just remember, beta is based on historical calculations and, as is often said, historical behavior is no guarantee of future performance!