Razz is a low-hand variation of Traditional seven card stud. Probably developed after a bunch of players had gone on long bad streaks and decided to flip things over so the worst hand wins to mix things up.  The game is played with 2-8 players. Most commonly played with fix limits and an Ante.  
 

All players ante to start the hand. Each players is dealt two cards face down (hole cards) and one face up (exposed) card. This is called third street. The person with the Highest exposed card must put money into the pot (effectively becoming the blind for you holdem players).  The High card can 'bring in' which is to bet half the small bet or this player has the option to "complete" making it a full bet. The other Players can then, raise, call, or fold in turn. Since low hands are best, the high card brings it in to stimulate action, and it does that very effectively.
 

Ex: Third Street		Forced Bring In
You	Opponent 1	Opponent 2

4th street: An exposed card is dealt to each player, followed by a round of betting. For fourth street onward, the person with the best exposed hand begins the betting (i.e. if someone has 76 exposed, another has 55 exposed, and someone else has 63 exposed, the person with 63 goes first because he has a 6 low.)
 

Ex: Forth Street	First To Act
You	Opponent 1	Opponent 2

5th street: An exposed card is dealt to each player, followed a round of betting. If the game is played in a fixed limit format, this is where the big bet would kick in. A big bet is usually equal to twice the small bet but this does vary.

Ex: Fifth Street                     First To Act
You	Opponent 1	Opponent 2