Actually when you have a dedicated server, you have all hardware resources allocated to your server. Inside this one, you can create several virtual servers called VPS (Virtual Private Servers or Virtual machines). To be able to achieve that point, you need to use virtualization. And there are several technologies to perform that. For linux, you have openvz, kvm, lxd, xen, virtual box for example. Then for windows, you have Vmware, Hyper-V.