Much like the game Breakout, the player controls the "Vaus", a space vessel that acts as the game's "paddle" which prevents a ball from falling from the playing field, attempting to bounce it against a number of bricks. The ball striking a brick causes the brick to disappear. When all the bricks are gone, the player goes to the next level, where another pattern of bricks appear. There are a number of variations (bricks that have to be hit multiple times, flying enemy ships, etc.) and power-up capsules to enhance the Vaus (expand the Vaus, multiply the number of balls, equip a laser cannon, break directly to the next level, etc.), but the gameplay remains the same.
At round 33, the final stage, the player will take on the game's boss, "DOH", a head resembling moai. Once a player reaches round 33, he must defeat DOH with his remaining extra lives because there are no continues on the final round.
The controls used by various conversions differ from machine to machine, and some conversions allow for multiple control methods. The two basic control methods are digital and analog. Digital controls (many joysticks and control pads, and keyboards) are considered less desirable than analog controls (most mice, trackballs, and paddles); while digital controls limit the player to single-speed control, analog controls allow the player to move the Vaus at nearly any desired speed across the screen. The NES version of Arkanoid was originally packaged with what's considered one of the rarest of all NES controllers, the Vaus Controller: a small gray controller featuring one button, a small spinner (with limited turn radius), an adjustment port, and the Taito logo. While the game may be played with the standard digital NES control pad, optimum gameplay is achieved with the Vaus Controller. Latter-day MAME arcade cabinet developers have created customized spinner controls to further simulate the arcade experience, although the Arkanoid controller had quirks which have made it difficult to achieve 100% reproduction.
Source: Wikipedia, "Arkanoid", available under the CC-BY-SA License.