Teaser bets are fairly similar to a parlay bet, in the sense that all teams selected must in order for the customer to win their bet. A single loss on any game will result in a losing bet. However, there is one big difference between a teaser and a parlay bet, and that is the customer is allowed to move the point spread in any direction for one particular game in their bet.
For example: if the Patriots are favoured by 10 points over the Giants, customers would have the option of moving the point spread in either direction. They could therefore make the new point spreads for the teaser bet; the Patriots -5 and the Giants +15 etc. However, with each sport there is a limit of how wide you can edit the point spread and the higher the point spread changes the lower your return on investment will be.