VM’s are mostly used in businesses and enterprises. The general idea is that you can take your hardware and divide it up into smaller chunks. Most likely whatever application you are running doesn’t need the power of a full server. Domain controllers are generally a good example. They only handle directories and user authentication (by default). Because the load is light, it makes sense to create a low spec VM just for it. You can make a VM for basically any application you want to run which is where the next part of VM’s becomes awesome. It’s super easy to migrate a VM between servers. In the event a physical host has an issue, you can just move the VM to another box and keep going. Its far faster than spinning up a new physical box.

I find VM’s have limited use for general users. They can make a great sandbox to test software that you don’t trust. They are also great for backwards compatibility. Unless you have a specific use for one I would avoid them though. Windows does have its “sandbox” feature built in if you want an easy solution.

Can you be more clear on what you mean by “storage medium?” Do you mean having an intermediary place to put files? This seems overly complicated for no gain.