e-Ink (eInk) is both a company and a technology which uses charged particles to produce an image (picture or text) on an electronic display. 
Once the display is ‘charged’ with the image, no current is needed to keep the image. So eInk technology uses very little battery power. e-Ink displays are not and do not need to be backlit. Backlighting on a computer or cell phone screen can be very hard on the eyes to read over a period of time, but eInk displays are as easy on the eyes as reading paper. In fact, because of the crispness of the display, some people claim the displays seem easier on their eyes.
The Amazon Kindle electronic book reader is one device that uses eInk technology. The Sony Reader uses the same technology in their electronic book reader.
e-Ink Corporation even sells a protype kit for developers to develop their own technologies with their eInk technology. The kit can be ordered off their website for $3,000.
Another exciting development with eInk is their partnership with Esquire to put their flexible eInk technology on the cover of their magazine. It will hit shelfs this fall.
http://www.msipublishing.com/blog/esquires-e-ink-cover-hits-shelves/