Hi, Annette. 4G LTE is a data plan offered through AT&T which allows your Kindle to work not only with WiFi but also with the AT&T 4G network. 4G is short for "fourth generation wireless communication." If you buy the Kindle Fire 8.0" HD 4G tablet, you can sign up for a 12 month data package with AT&T for $49.99. At the bottom of the page showing the information about the Kindle Fire HD 8.9" 4G LTE Wireless Tablet is information about this data package.
The Kindle Fire 8.9" HD tablet does not have the option of working with a cellular network. If you don't need the speed, additional storage, etc., the Kindle Fire 8.9" HD would probably be your best bet. Keep in mind that the higher the gigabytes (i.e., 8 GB does not offer as much storage as 16 GB), the more storage space you have on your tablet.