This article explains a trick, almost like a magic trick. The aim of this trick? To deceive our computer into thinking that it is inside another computer, equipped maybe with another operating system. Why do we do that? For numerous reasons. Some of the possible reasons include: to be able to run multiple applications on one server, to be able to simultaneously run multiple operating systems on one computer, to be able to run multiple sessions of a single operating systems or just to be able to host applications that are incompatible with our host operating system. The reasons are numerous, the solution is elegant. Let’s see then what is virtualisation and how it is achieved!