Seven-card stud is played with two downcards and one upcard dealt before the first betting round, followed by three more upcards (with a betting round after each card) and one more downcard. After the last downcard is dealt, there is a final round of betting. The best five-card poker hand wins the pot.
In Texas Hold 'em, having 2 and 7 off suits is rated the worst hand. This is because they're the two lowest cards you can have, and they can't create a straight (there are five cards between 2 and 7).