Prøv før du installerer
A LiveCD can be put into the computer, and then the linux operating system that is on the CD will run on your computer from this CD without changing your computer in any way - neither the configuration of it, or the data you have lying on it. This makes it possible to test the new operating system without "touching" your computer.
Some Linux versions offer a decidedly LiveCD, while others allow you to try the operating system from the installation CD before any installation.
Same opportunity to try Linux as with the LiveCD - but with the difference that the data on the USB stick can be changed, ie there can be written to and stored on the USB stick. So, besides that you can try linux operating system, you can then also use it right and save the stuff you're doing on the USB stick. So, besides the possibility to test an operating system, you get a "portable" oprerating system that can be taken into the pocket and used on multiple computers.
Note: On some computers, especially older ones, you can not boot from a USB stick - ie it can not be used. Here one must use a LiveCD instead.
Wubi is an Ubuntu installer designed to make it easy for Windows users to try Ubuntu. When you put your Ubuntu CD or Ubuntu USB stick into your computer while Windows is running, the Wubi (which is part of Ubuntu) ask if you want to "install" Ubuntu.
It works by Ubuntu gets installed in a file in the Windows file system (instead of, as usual, to be installed in its own partition alongside Windows partition). Ubuntu comes then to be like any other program in Windows, and therefore modifies nothing on the computer's setup.