Purikura generally cost 300 or 400 yen in Japan. You stand in front of a blue (or green) screen and pose for dozens of photos (within a time limit). People usually take cute or silly poses.
When you're done you have a few minutes to add effects and graphics to your photos. Each machine has a different theme.
Modern purikura can make your eyes appear larger and perform other beauty-salon-type transformations.
Purikura came out in 1995. They were an instant hit with teenage girls. In the late 90s, high school girls all over Japan collected huge binders of purikura. Sales (of machines) peaked in 2002 and have been in decline since. Purikura face increased competition from mobile apps.
Purikura are found at Japanese arcades, theme parks and shopping malls. Small purikura shops can also be found in youth-oriented shopping areas such as Shibuya.
Lone men aren't allowed to enter most purikura. This is to protect purikura's clientele (who are primarily young girls). Couples and groups of young men are generally allowed to enter. Purikura are popular amongst couples in Japan.
In order to combat declining sales, many purikura now offer additional services such as costume rentals.
Japanese purikura manufacturers have had great success selling machines in Asia — especially Korea, Taiwan and Singapore. They've also had some success selling machines to the US (sales in Europe were a flop).
Although sales are in decline — purikura machines continue to evolve and innovate. They're still fairly popular with teenage girls in Japan. New purikura machines work with mobile apps to share photos on the cloud and social networking sites.
It's common for tourists to give purikura a try. It's a recommended Japan travel experience.