Cricket is a bat-and-ball team sport and the national sport of England. The game has spread across the world from the expansion of the British Empire. However, to countries that have not been in the British Empire in the past century, cricket may seem a bit complex.
Comparing cricket to baseball elucidates the rules and nature of the game. Much of understanding cricket is getting past the terminology, which can be easily done by translating between baseball and cricket terms.
Definitions - Cricket rules are known as the Laws of Cricket. Teams are called "sides." Scoring is called a "run." A match is called a "test." In a match, each side is up twice. A side's being up constitutes an "inning," as contrasted to baseball, in which it would be called a half-inning. The bat used is relatively flat compared to a baseball bat, but not as flat as a ping-pong paddle. Swinging with the bat is called a "stroke." A "four" and a "six" is a hit outside of the cricket ground that earns four and six runs, respectively. They are also called "boundaries," because they fall outside of the boundary of the cricket ground. In cricket, the ball is "bowled" by "bowlers," not thrown by pitchers.
Batting - In cricket, two batsmen are up at once. They take turns batting when they switch places to score a run (explained later). The one who swings the bat is called the "striker," and is said to be "on strike." The two batsmen bat until one of them is made out. He is replaced by the next batsman in the batting order. Each side has 11 players. Since one player can't bat alone, the batting order is exhausted and the inning is over when 10 men are out. The ball can be batted in any direction, unlike baseball, in which the ball direction is restricted to a 90-degree range.
Locations on the Field - The two batsmen stand at opposite ends of the "pitch," an area 66 feet by 10 feet. The pitch is in the center of the "cricket ground." A "boundary" is designated (sometimes with rope) around the cricket ground. If the batsman hits a ball past the boundary, runs are automatically scored. When receiving a bowler, a batsman stands near his wicket, which consists of three long stakes in the ground ("stumps") with two short pegs ("bails") balanced on top. The bowler's aim is to hit the wicket, to make the batsman out. Being the target of the bowler, the wicket is the equivalent of a strike zone in baseball.
Scoring - Batsmen score by switching places on the pitch while fieldsmen try to return the batted ball to the center of the field. Switching places scores a run. If they have time before the ball is returned, they switch places again to score another run. If the ball is hit out of the cricket ground, four runs are automatically scored without the batsmen having to switch at all. If the ball is hit out of the cricket ground without touching the cricket ground (a fly ball, in baseball), six runs are automatically scored. "Fours" and "sixes" are also called "boundaries."
Penalties - A batsman is finally out when a hit is caught before it hits the ground (a fly ball) or a bail is knocked off a wicket, either when the bowler is bowling or when the batsman is switching places with the other batsman. (Hitting the wicket is analogous to tagging with the ball in baseball.) Since the batsman does not have to run after hitting the ball, he may strike the ball merely to keep it from hitting the wicket. In baseball, getting hit by a pitch earns a walk, but not if the batter steps outside the batter's box. The analogue in cricket is that if a bowl would have hit the wicket but instead hits a body part the batsman used to defend the wicket, the batsman is out. There are more ways to be made out, and plenty more terms and rules (e.g. running pitches are allowed, but not with a bent arm), but the above gives a good introduction to the nature of the game and its most important rules.
Common Phrases of Cricket Origin - Common phrases that originated from cricket include "knocked me for six," "different strokes for different blokes," and "Howzat?" "Howzat?" is a question asked by a bowler of the umpire to ask if a bowl took the batsman's wicket. The "different strokes" phrase derives from the specialization of batsmen in different swing styles, partially owing to the omnidirectional nature of a legal hit. The phrase "knocked me for six" is equivalent to saying, "I was bowled over, or shocked." It derives from the unlikely play of hitting a ball out of the boundary without touching the cricket ground.