Draw on the board with the right mouse button: click a square to mark it, drag to draw an arrow. Hold Shift, Ctrl or Alt for other colors.
The engines play each other while you watch. Colors switch every game.
Blizzard plays a series of games against Stockfish at the strength you choose, and you see how many Elo points stronger or weaker it is. Openings come from the book, and each one is played with both colors.