The way you bet a football game is that the odds maker will pick a winner and how many points the winner must win by. The idea behind this is that if the odds maker has found the perfect 'point spread' (or points one team must win by), bettors will pretty much bet 50/50 across the wager.
Here's an example: This weekend the Steelers played the Bengals in the wild card match up. Odds makers said that the Steelers had to win by more than 3. Thus, the idea is that oddsmakers think that 50% of the bettors will bet that the Steelers will win by 3 while 50% will bet that the Steelers won't win by that much or possibly not even win.
If you take 2000 people betting this way, it looks like this:
1000 bet $11: Steelers by 3
1000 bet $11: Bengals "Beat the spread"
All tolled, the bookie (or bet taker) takes in $22,000
Now... this could go one of 3 ways:
1) The Steelers win by lots (at least more than 3)
2) The Steelers win by 2 or less or even lose
3) The Steelers win by exactly 3
In cases 1 & 2, The group that bet correctly gets their $11 back + $10
This pays out $21,000 to 1000 bettors. Thus in a perfect 10:11; The bookie makes $1 for every 2 bets on either side of the line.
This of course can backfire. If 4 days before a game 3 star players are killed in a car crash, it's pretty obvious that team won't play as well. Usually at that point the odds/spread will change. All future betting will be at the new spread/odds.
3 weeks ago the Steelers were 22:1 to win the Superbowl. Now there are only 8 teams left and the Steelers are among that group, they are now 12:1 to win. (Bet 1 get 12 back)
So... What about this word, "Parlay".
In Horse racing we have the trifecta. This means not only picking the winner but the 2nd and 3rd place. Since it is placing multiple bets... it raises the odds.
In sports betting you can lump multiple bets together. It raises the odds but also raises the possibility you will lose.
So looking at the past weekend's football I bet the following parlay:
(201) Washington Redskins +3 (-130) Sat@1:30
(204) New England Patriots -7.5(-115) Sat@5:00
(207) Pittsburgh Steelers -3 Sun@1:30
Now we get math...
An evenly matched odd is 1:1, that would pay $1 for each $1 spent. Or $2.
So the multiplier is 2
Let's say the odds are 4:5, this would pay $0.80 for each $1 spent: $1.80
So the multiplier is 1.8
So the numbers in parens above are the odds in amt to bet to win $100.
Washington is Bet $1.30 to win $1. or bet $1 to get $0.76
The multiplier is 1.76
So we take 1.76 * 1.86 * 1.90 (assume -110 if not listed) = 6.21984
Thus had you bet a $10 parlay this way, it would have returned $62.19; So you would have won a little over $50