Its copy and paste source : ubuntu.com Xen is a software which makes possible for you to use two different operating systems on your laptop without having a need to reboot from one operating system to another. Xen is also the name of technology which makes this possible. Hence it is some times confusing as when some one is talking about Xen or when some one is talking about the technology. For example you when use your computer you can always open up Firefox and browse websites imagine a situation similar to this one where without rebooting into another operating system you can use Windows or any other operating system from within Ubuntu i.e. you do a click select on some application and are able to use the Windows or Solaris or another operating system while still working on the Ubuntu at the same time. Xen is mostly used on servers but it is possible to use at your home computer also. There is other software available comparable to Xen. Some of them are proprietary such as VMwar
No matter how sophisticated the technology is , It still takes people !