There are now many ways to enjoy eBooks. You don’t need an official Kindle or Nook device—you can read them on a computer, a smartphone, or a tablet. You may need to add a program (or “app”) to do so, but the same “app” is available for most devices. Thus, a generic “tablet” (Samsung, etc.) plus an app equals a very pleasant way to read. You can adjust colors, contrast, font size, etc. to your individual needs.
For the totally uninitiated, may we suggest “practicing” with your local library. Most libraries now have a digital book division, with instruction and help available. They may a require a reader app you can only use with them, but you will become familiar with the process.
There are many sources for eBooks. Commercial ones include Amazon, Barnes & Noble, Apple, etc. After purchase, you “download” a copy of the book to your device to read. To read a book purchased from Amazon, you either need their Kindle tablet or their (free) Kindle reader app for your device. eBooks purchased from most other commercial sites can be read with a variety of 3rd party reader apps.
Many free eBooks are available, especially public domain older works from such legitimate sites as Project Gutenberg. At best, these sites’ offerings often lack professional formatting; at worst–from “if-ier” sites–you could be cheating legitimate rights-holders and/or asking for malware.
If you use the Firefox browser, you may read the .epub format directly via the EPUBReader add-on.