Definitions for: F
Favourite
Oposite: Underdog.
Fractional odds
Example: odds of 1/3 mean that bettor wins 1 unit for each 3 units staked (thus equal to 1.333... in decimal format), and 2/1 mean that bettor wins 2 units for each unit staked (thus equal 3.00 in decimal format).
Some fractional odds have their fancy slang names: Evens, Carpet, Double Carpet, Burlington Bertie, etc; for more details, see http://en.wikipedia.org/wiki/Tic-tac.
See: Odds.