An e-book is a digital version of a book that can be read on computers or electronic devices. E-books differ from printed books in that they require electronic devices to read and do not use physical paper. Some key advantages of e-books are that they are cheaper and more portable than printed books since they do not require carrying physical copies and can be accessed from any internet-connected device. However, e-books also have disadvantages like requiring a power source and potentially causing health issues from overuse like eye strain.