What is the purpose of the Walmart's stock performance chart in their annual report 2020?

This graph compares the cumulative total shareholder return on Walmart's common stock during the five fiscal years ending through fiscal 2020 to the cumulative total returns on the S&P 500 Retailing Index and the S&P 500 Index. The comparison assumes $100 was invested on February 1, 2015, in shares of our common stock and in each of the indices shown and assumes that all of the dividends were reinvested

As per the discription given by walmart, chart represents earning of shareholders in relation to S&P 500 Index and S&P 500 retailing Index, it shows year by year earning growth of share holders by taking 100 as base year