Beta is the measure of risk or volatility of a stock or a portfolio compared to a benchmark or index fund that represents the entire market. In a nut shell beta will indicate if the investment is more or less volatile than the entire market. Beta would indicate the risk of investments that can’t be reduced by diversification, it doesn’t measure the risk on a standalone basis of that investment rather the risk it adds to an already diversified portfolio.
Generally, a market portfolio would be represented with an exact beta of 1. A Beta below (-1) would mean that the investment has lower volatility than the market or that the investment is not highly correlated with the market movements. A Beta greater than 1 would usually indicate that the investment moves up and down with the market and can even magnify those trends.