Seeing as there is no such thing as Qlikview Cloud I'm guessing you might mean Qlik Sense Cloud (https://qlikcloud.com)? Alternatively I guess you may mean running QlikView "in the cloud" as many customers do?
Qlik Sense Cloud is not "a cloud" as such, it is a cloud hosted (using AWS infrastructure) and available Qlik Sense platform that allows you to use a tailored form of Qlik Sense in a secure, managed environment. It doesn't differ from "other" clouds, it is "in" the cloud. You can use it in different ways depending on the level of subscription you desire, but you can try it for free and see whether it might suit you as a starting point. Your only system requirement is to have a web browser and internet connection. More information is available at Qlik.com
Using QlikView in the cloud is simply a matter of installing QlikView in a cloud hosted environment such as AWS, Azure or many others. There are various Qlik partners who can facilitate this for you though many customers choose to manage this themselves.
Hope that clarifies things for you. I'd also suggest reading the information on this page: Cloud computing - Wikipedia