The Qi wireless charging standard from the Wireless Power Consortium (WPC) is having a relatively good year. Now is a good time for a bird’s-eye view of the technology—how it works, what it’s for, and what its prospects are. This is also a good time because millions of Apple ecosystem users are about to get their first sampling of Qi when the iPhone 8 and iPhone 8 Plus launch this Friday.

Qi has appeared in phones of various stripes for more than five years, and many people are already using it. The basic tech has been used for consumer products like razors and toothbrushes for a while, plus a variety of non-consumer tools.

Even if you haven’t used Qi, you may have seen Qi wireless charge pads at airports. In 2014, Verizon installed Qi wireless charging stations in several US terminals, from JFK to LAX. You’ll find them in plenty of other places, too, including devices like the Samsung Galaxy S8 and the US version of the LG G6.