With both the VPS and dedicated servers, you have full control over the entire server environment. You can add users, install any software, configure it anyway you want to.
The big difference is with VPS, your entire server environment is on a single physical machine along with other people's server environments. Nobody can access each other's environments. But you are sharing physical resources -- hard disk, memory, CPU.
With a dedicated server, your server environment is on a single physical machine with no one else. So you get all the physical resources (hard disk, memory, CPU) to yourself.
█ ServerSea – Low Cost High Quality Hosting
█ Free Domain
, 99.9% Uptime, Super Fast Servers, Backups, True 24/7 Support
█ Money Back Guarantee, Special Discounts