Long off is the name of the fielding position a long way away from the batter, near the boundary. Therefore the "long". The "off" referes to the fact that the position of the fielder is the same side as the position in which the batter holds the bat. The fielder in the same position, but on the opposite side is called long on.

Cricket is played by two teams, of 11 players each, one team fielding and one team batting. The game is played on an oval field with a 22-meter long pitch in the middle. At either end of the pitch are three hip-high posts called wickets. The batter protects the ball from hitting the wickets by hitting the ball with a bat. A bowler from the fielding team runs up from one end and bowls the ball to the batter at the opposite end. The batter gets a run every time he hits hard enough to have time to switch ends with the other batter.

The short 20-over game has become popular recently and is loved for its high speed and excitement. 50-over games lasting a day and 3 and 5 day games also exist.

More Info: en.wikipedia.org