Cloud Hosting and Shared Hosting

Hello guys!
I was looking for a good host.
Wandering in The web Hosting sites, I found that many hosting sites are offering Cloud Hosting and 100% Up Time
What is Cloud Hosting? and
Is it possible to give 100 % up time?
I am a newbie here.
I really thank you all for your support.

The question of what cloud hosting is has been discussed regularly in this forum before, as has the topic of recommended hosts. If you do a search here for ‘cloud hosting’ you’ll find plenty opinion on what cloud hosting is.