This is a bet which most gamblers think is easy to win but in fact this bet is altered in the casino favor with a house edge of 5.56% and this isn't an attractive number.
To make this bet you need to place your chips in the area labeled field, along with a whole slew of numbers, but those numbers aren't choices. When you bet on the field you bet that the next roll will be a 2, 3, 4, 9, 10, 11, or 12. If a 3, 4, 9, 10, and 11 is rolled you are paid even money and if a 2 or 12 is rolled usually you are paid at 2:1.
Some casinos pay 3 to 1 for 2 or 12, but not usually for both, just one or the other. If a 5, 6, 7, or 8 are thrown then you lose. These are of course, the more likely numbers, so my advice is to don't play the field.