You have to play to win but you may lose. It is safer to just stand around and watch.
Some people just kibbitz.
"English actor Joseph Crowell reported that the game was played in New Orleans in 1829, with a deck of 20 cards, and four players betting on which player's hand was the most valuable. Jonathan H. Green's book, An Exposure of the Arts and Miseries of Gambling (G. B. Zieber, Philadelphia, 1843), described the spread of the game from there to the rest of the country by Mississippi riverboats, on which gambling was a common pastime. As it spread north along the Mississippi River and to the West during the gold rush, it is thought to have become a part of the frontier pioneer ethos."
The above quote is from the wikipedia page on poker linked below.
http://en.wikipedia.org/wiki/Poker
