Virtual Machines (VMs) is 1960's technology. Started out on the mainframes.

x86 virtualization came along in the 1990's. VMware Desktop everybody knows today was released around 1999. Other players have been around.

This is the same year jails was introduced with FreeBSD 4.

The funny thing is that jails are often referenced as "virtualization without the overhead".

Jails are really fast as it is the same shared kernel. Hardware VMs have additional security advantage as a guest kernel vulnerability will (normally) not affect ofter guests. But it comes at a cost.