The price-to-earnings growth (PEG) ratio is a financial metric used by investors to evaluate the relationship between a company's stock price, its earnings per share (EPS), and its growth prospects. It is a variation of the traditional price-to-earnings (P/E) ratio that takes into account the company's expected earnings growth.

The PEG ratio is calculated by dividing the P/E ratio by the projected earnings growth rate. This ratio provides a more comprehensive assessment of a company's valuation compared to just the P/E ratio. A PEG ratio below 1 is typically considered favorable, indicating that the stock may be undervalued relative to its earnings growth potential.

Investors use the PEG ratio to identify stocks that may be priced attractively based on their growth prospects. A low PEG ratio suggests that a company's stock price is relatively cheap compared to its expected earnings growth, which could indicate an investment opportunity. However, it's important to consider other factors and perform thorough analysis before making investment decisions solely based on the PEG ratio.

It is worth noting that the PEG ratio has limitations and should not be the sole determinant in investment decisions. It relies on projected earnings growth, which can be uncertain and subject to change. Additionally, different industries may have varying typical PEG ratios, so comparisons should be made within similar sectors. The PEG ratio is just one tool among many that investors use to assess the value and growth potential of a company's stock.