In finance, 'beta' quantifies the systematic risk associated with a particular stock in relation to the entire stock market. A beta value greater than 1 indicates higher volatility compared to the market, while a value less than 1 suggests lower volatility. This measure is crucial for investors in portfolio management, as it helps in assessing the potential risk-return trade-off of their investments and aids in making informed decisions based on market conditions, aligning with the financial principles outlined in standard UPSC materials.