How does the International Space Station make oxygen?

I found this article at Space.com (see link in related links) I hope is helps.

"Built by Russian engineers, the Elektron device aboard the space station uses electrolysis to separate water into hydrogen, which is dumped overboard, and oxygen. The 1,500-pound (680-kilogram) OGS rack works in much the same way, and will be able to provide 12 pounds of breathable oxygen daily under normal operations, NASA officials said."