Fun Fact: The pack-in Vaus Controller is now one of the rarest NES controllers ever made.
Arkanoid features the same basic mechanics as Breakout: you control a bar at the bottom of the screen and bounce a ball into a wall of blocks to destroy them and move on to the next level. Arkanoid took that idea and added powerups like the ability to stretch the bar out, to catch the ball or slow it down.
The best powerup was the laser, which played into the somewhat-ridiculous idea of trying to wrap a science-fiction storyline around the game. Lasers could destroy blocks as well as the little alien spaceships that would float around the playspace. The NES version came packaged with a special controller that served as a stand-in for the original arcade controls.