Why is my yield not my return on equity?

I just got the statement from my Vanguard 500 Index Fund.
Under “Portfolio Characteristics” it says that its Return on Equity is 19.6% but the Yield is 1.7%.
What gives?
What’s the difference between RoE and Yield?

ROE is net income divided by shareholder equity.

This site gives a more detailed explanation of different concepts of “yield.”

Basically, the difference is based on how re-investment of earned cash (instead of distributing it to the investor) is included in the calculation.