The term "e-book" is short for electronic book, which is a digital book designed to be read through a mobile or portable e-reader device. As of 2014, people can purchase e-books through online retailers, download the books to their e-readers and then read the content immediately.
Common formats for e-books, as of 2014, include .TXT, .PDF and ePub. Some devices only allow people to read e-books using certain formats. Applications are available that allow users to convert a book from one format into another. E-books are offered as a digital version of print publications or as the sole source of book distribution.