How do you explain Virtualisation?

I was just reading “Cisco’s Billion-Dollar Server Guy Has Left“, over at Business Insider, and it explains Virtualisation as:

“virtualization software tricks applications into thinking they are on their own servers, even though they are sharing one with many others”

Which is an interesting take; although I think the use of “tricks” makes it sound a lot more hacky/dodgy than it really is.

As a Virtualisation enthusiast, explaining Virtualisation to a non-technical audience has always been an interesting conundrum for me.

How do you explain Virtualisation “in a nutshell” to non-techies?