Amazon has 3 different types of e-readers on the market:
Kindle — 6-inches
Kindle Paperwhite — 6.8-inches
Kindle Oasis — 7-inches
The basic Kindle has 300 ppi, 16 GB storage, and isn’t waterproof. The Paperweight and Oasis come with larger storage options, 300 ppi, and are waterproof up to 2 meters.