Amazon.com's Kindle devices are primarily for storing and reading e-books. Some Kindle devices run the Android operating system and can run Android apps similar to a tablet, and Kindle reading software is also available for most computer and mobile device operating systems.
Amazon.com introduced the Kindle in 2007. The initial device was used for e-books, magazines and audio files such as books on tape. Early Kindle devices could only display e-books in grayscale and required users to obtain them through the Kindle Store on Amazon.com. With the Kindle DX in 2009, support for PDF files was added.
The Kindle Keyboard, released in 2010, added a small attached keyboard to the unit as well as Wi-Fi support. The Kindle 4, released in 2011, switched to a virtual on-screen keyboard and added a new Web browser.
While technical improvements have continued with new Kindle releases, little in the way of new services have been added to the basic e-readers as of 2015. The Kindle Fire line was first released in 2011 and added the Android operating system and touchscreen functionality of a standard tablet.
The Kindle applications for various computer and mobile device operating systems allow access to e-books purchased through Amazon.com.