Im kinda confused about hosting. whats da difference between virtual, shared and dedicated hosting?

Dedicated hosting is. When the server is only for you and your site(s)
Shared is when you share the server with somone else

What ya need depends on what kind of site ou have

If i got my website set up on one host and then decided i wanted to change, would i have to reintegrate everything (ie.template and oscommerce) or could i somehow just upload the entire site onto my new host?

Im not sure about the whole site, but u can do page by page. view the source of your web page, copy it upload to your host with all the files and pics. hopefully it works

Privided your new host has the same features and similar setup the migration from one host to another should be fairly easy. All it would require is uploading your files and then just verifying the pths to the applications you use. That and changing nameservers.

If your current host has cpanel then u should be able to just backup everything and re-upload it at the new host. MYSQL Databases you will need to do seperate, however.