What is hotspot?

[Cool]

A hotspot on a cell phone allows any WiFi enabled device to use the internet provided by your network provider on mobile. For example if you are using AT&T and you have internet bucket enabled in your contract, then you simple turn on the Data traffic on mobile, then go to settings>more..(under Wireless & Network heading)>tethering & portable hotspot>portable WiFi hotspot. First time use requires configuration, set it up and turn on. And after it is turned on, you can connect any device, including Kindle Fire, Laptop or computer with WiFi to it and use internet on that device. SO the answer to your question is "Yes, you can use internet on Kindle Fire connecting it to WiFi hotspot of your smartphone"

=Shld i just splurge and have wifi installed at home? Do I have to have a land line to have wifi?
If you can install, it would definitely provide you with better speed. There's no requirement of landline in case of broadband providers.

Before getting the Kindle Fire, you need to know what makes it the best option, take a look here at this discussion:
http://compare-e-readers.com/IsHdxGreat

The Kindle Fire HDX is the best option to go for, you can find every feature on it to be really good, I.e the quad core processor, full 1080p screen, dual WiFi antenna providing with better speed, the Digital Dolby audio speakers provide you with awesome sound quality and features like "Mayday" make a technician available to you 24*7 right on your screen real easy.

Hope this helped!