Consolidation vs Virtualisation
In consolidation you put multiple applications into a single server. In the traditional unix world, that was easily achieved (and still is) because the system is securely segmented.
In virtualisation, you create virtual environments which imitate what an application would get if it were on its own.
You can consolidate into a server which is a single operating environment or multiple virtual environments.
It is all now soooo confusing because of the numerous degrees of separation available: whole server, hard partition, soft/logical partition, hypervisor layer, containerisation and plain old apps sitting next to each other.