Ubuntu is an operating system built by a worldwide team of expert developers. It contains all the applications you need: a web browser, office suite, media apps, instant messaging and much more. Ubuntu is an open-source alternative to Windows and Office.
New Ubuntu can be run directly from CD / DVD or USB flash drive without any installation or changing your system settings. However, performance is bit slow because it runs from CD/DVD drive. You can use for a while and then decide whether it is suitable for your requirements and you wanna install on your system for faster and better performance and stability.
What is Live CD ?
Live CD is pre-installed Ubuntu OS, which will be run from CD drive and do not required to install on local system.
How to get Live CD ?
You can download the Ubuntu ISO file free from http://www.ubuntu.com/GetUbuntu/download and burn using any software.
Alternatively, you can order the free CD from https://shipit.ubuntu.com/ This might take few weeks so if you have high speed internet connection then just download and burn.
How to install / run ?
Put the Ubuntu CD into the CD/DVD-drive and reboot the computer and make sure that boot device is selected as your CD/DVD-drive. You should see a menu with "Try Ubuntu without any change to your computer" at the top.
Select the language of your choice.
To begin with use the first option so this will not change any of your system settings and run the OS from CD/DVD drive.
Try for some time and see if the new OS is suitable for your all requirements. Normally, it will automatically installed drivers for your Graphics, Sound, Wi-fi, Ethernet, etc and you should be able to use the OS just like new Windows.
P.S : When you shutdown your PC, at this point anything you saved to the desktop or Documents folders and such will vanish - only things you saved into folders on the hard-drive will remain.
Once you decided to install the OS then simply restart the system and select the "Install Ubuntu" option.
You may want to edit your partition before installing Ubuntu on your HDD.
Source : https://help.ubuntu.com/community/LiveCD - visit for more detail and how to create custom Ubuntu CD/DVD/