A poker variation of 7 card stud in that the pot is split between the High hand, and the Low hand. In order to make a "low" one must achieve a hand with 5 "unpaired" cards below the value of 8, which may include aces. An interesting phenomenon occurs when the low hand also becomes the high hand; and is referred to as "scooping" the pot. This can happen in a variety of ways, such as achieving 3 of a kind, a straight, a flush, or even pairs in addition to the low. On occasion no low hand is made which results in the pot being "scooped" by the best high hand as in normal 7-card stud. One additional difference between 7 hi/lo and traditional 7-card is the ante structure. In this game there tends to be a "bring in" bet, this is a "forced" bet placed by the low card at the table and is usually of the minimum allowed bet for the table.

Sources, and further reference material:
The Theory of Poker: by David Sklansky
High-Low-Split Poker: by Ray Zee