Wow...WGT players took over 100,000 virtual Mulligans last week!
A Mulligan allows you to retake any golf shot in the game, so you can practice and perfect those especially challenging ones, or redo a shot you don't like.
The free Mulligan feature is currently available in practice rounds for single-player stroke play games only, so Mulligans don't impact any of your ranked stats. Note that Mulligans do count as an extra hit on the virtual golf ball that you're using.