A e-reader is a mobile device designed primarily to read digital books. Kindle and Kobo are e-readers, which can read ePub or PDF formats for example.
Is it possible to upload ePub and PDF format on my Kindle or on my Kobo to read eBooks ? Answer is yes for both Kindle and Kobo
How to add ePub, PDF, docx... books to your Kindle: 5 easy ways to do it without any IT experience