Hello ihateicloud12,
I can appreciate why you would want more information on this. The "cloud" is basically a computer on the internet that your username and password gains you access to. Any device (computer, phone, TV, etc) that can authenticate your properly and display your content has access to that data.
This gets confusing quick. The way I look at it is that the cloud is the mother ship and the other devices are just baby copies. If you log into icloud.com and delete everything from there (please make sure you have downloaded a copy of your content before), your basically logging into the mother ship command console and deleting it from the master record (insert independence day meme). All other devices will then follow suit with the exception of iCloud messages.
Here are some articles that may help
Archive or make copies of the information you store in iCloud - Apple Support
Download iCloud for Windows - Apple Support
Download iCloud photos and videos - Apple Support
What is iCloud? - Apple Support
Introduction to iCloud - Apple Support
Thank you
Mikel Smart