What is 'alpha' in equity investing?

Alpha is an estimated value of a stock's expected excess return. Simply put, alpha is the difference between the investment return and the benchmark return (eg. NSE Nifty) or what the scheme generates over and above the returns of its benchmark index.

from Wealth-Economic Times https://economictimes.indiatimes.com/wealth/invest/what-is-alpha-in-equity-investing/articleshow/78461114.cms