Your Linux distribution of choice probably allows you to use it in a "live" environment, meaning it runs entirely off the disc or USB drive and doesn't actually need to be installed to your computer's hard drive. Just use the Linux desktop normally and get a feel for it. You can even install software, and it'll remain installed in the live system until you reboot.
Even if you don't want to use Linux as your everyday operating system, having this Linux live DVD or USB drive around can be useful. You can insert it into any computer and boot Linux whenever you want. Use it to troubleshoot Windows problems, recover files from a corrupted system, scan an infected system for malware, or provide a secure environment for online banking and other important tasks. Another handy trick: If you enable the "persistence" option when putting Ubuntu on the USB drive, you can save files and settings to the drive and they'll remain accessible every time you boot it.
To leave the live Linux system, just reboot your computer and remove the disc or USB drive.
Feel your way around
Depending on which Linux distribution and desktop environment you choose, your desktop environment and installed applications will vary — though most will cover your typical needs. Most Linux distributions ship with the Firefox web browser, for example, and Google's Chrome or the open-source Chromium browser are just a few clicks away.
Your desktop environment should have all the standard bits: an application menu, some sort of taskbar or dock, and a notification area or "system tray." Click around to see what everything does. You should also find a collection of system configuration utilities, which will let you configure your hardware and make your desktop work the way you'll like it.
Ubuntu's Unity desktop can be quirky, but it's packed with useful features you'd never find on your own, like the HUD. Read my Ubuntu guide for displaced Windows users for more details. Be sure to enable virtual desktops (most modern Linux desktops have disabled them by default) and give them a shot, too. (Windows users are about to discover how useful they are in Windows 10).
Install Linux, or not
You have choices about when and how to install Linux. You can leave it on a disc or USB drive and boot it up whenever you want to play with it. Play with it several times until you're sure you want to install it. You can try several Linux distributions in this way — you can even re-use the same USB drive.
The big reasons to install Linux instead of just running it from a USB drive or disc are productivity and convenience. Unlike running Linux live, installed Linux will remember your settings, keep your installed software, and maintain your files between reboots.
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