A parlay basically works like this:
For example:
You bet XX amount of dollars that henrik, david wise, and bobby brown will all win. To win the parlay, all 3 people would have to win. The odds of you winning are lower than just betting on one person, because every person has to win.
Normally parlays include 2-10 different bets and you have to win every bet to get the money.
The idea is bet a small amount, and win big.
Bets in parlays do not all have to be in the same sport.
Example 2.
Odds on Detroit red wings winning a specific game: 1/2
Odds on Chicago blackhawks winning a specific game: 1/2
If you were to do a parlay bet with both games, the odds would be something like 1/4 or 1/5 that both teams win their respective games.