As you walk the streets and shopping districts of Japan, you may stumble upon odd looking vending machines. These are no ordinary dispensers with foreign objects inside. They are in fact gacha, short for gashapon machines. By putting money into the machine (varies from ¥100 to ¥300 or $1 to $3) and turning the knob, a random plastic capsule comes out containing a mystery item. Each gacha machine has a theme of items available inside. The various items are displayed on the machine and can include stickers, figurines, pins, key chains, and other trinkets. Gacha machines are a game of chance that entices people to play multiple times to collect a specific item or set. Gacha items can also be purchased from hobby shops found in places like Osaka's Den-Den Town or Tokyo's Akihabara.
The images above show a gacha machine that contains eight key chains from the Attack on Titan anime series. Putting ¥300 into the machine and turning the knob resulted in a Mikasa key chain. It was a lucky pull because Mikasa is one of the most popular characters in the show. You can find gacha machines scattered everywhere around hobby shops, conbinis, Don Quijote, Pokemon Centers, and other shopping locations.
The gacha mechanics are also found in video games such as the new Nintendo mobile release, Fire Emblem: Heroes. Here is a great article that highlights gacha found in the game. Try not to spend all of your loose coins next time you come across a slew of gacha machines.