Choose "BTTS Yes" if you expect both teams to find the net. Choose "BTTS No" if you expect a clean sheet by at least one side.
BTTS Yes wins on scores like 1-1, 2-1, 3-2, 1-4. BTTS No wins on scores like 1-0, 0-0, 2-0, 0-3.
You pick BTTS Yes on Arsenal vs Chelsea. Final score 1-1. Bet wins!