Decimal: Total return per unit staked. 2.50 = win 1.50 per 1 staked.
Fractional: Profit / stake. 3/2 = win 3 for every 2 staked.
American: +150 = profit 150 per 100. -200 = stake 200 to win 100.
Implied %: The probability the bookmaker implies for this outcome.