From Wikipedia:
"Pachinko (パチンコ?) is a type of game originating in Japan, and used as both a form of recreational arcade game and much more frequently as a gambling device, filling a niche in gambling in Japan comparable to that of the slot machine in Western gambling. A pachinko machine resembles a vertical pinball machine, but has no flippers and uses a large number of small balls. The player fires balls into the machine, which then cascade down through a dense forest of pins. If the balls go into certain locations, they may be captured, and sequences of events may be triggered that result in more balls being released.[1] The object of the game is to capture as many balls as possible these balls can then be exchanged for prizes. Pachinko machines were originally strictly mechanical, but modern ones have incorporated extensive electronics, becoming similar to video slot machines.
The machines are widespread in establishments called parlors, which usually also feature a number of slot machines (called pachislo or pachislots); hence, these venues operate and look similar to casinos. Modern pachinko machines are highly customizable, keeping enthusiasts continuously entertained. Because gambling for cash is illegal in Japan, balls won cannot be exchanged directly for money in the parlor; instead the balls are exchanged for tokens or prizes, which are then taken outside and exchanged for cash at a place nominally separate from the parlor.
As an indicator of the popularity of pachinko in Japan, the Japanese government estimates of the annual revenues of the pachinko and pachislot industry is in the region of ¥29 trillion (US$300 billion)[2]."
So basically equivalent to our slot machines, but probably more interesting!