A live USB flash drive is just a regular USB flash drive with a full bootable operating system on it. Linux is the usual choice of operating systems. With a live USB, you can plug it into your notebook or desktop, turn it on, press F12 and choose to boot from the USB device in the displayed list. In just a short while, you have full control of your system even if you otherwise had serious booting problems (a crashed hard drive, a virus infected Windows system, etc.). It’s a great way to do several things. You can use it to access files on a crashed system (this is more difficult on systems that boot with Windows 8 or 10, but still doable). You can use it to upgrade your experience online if the system you are using had been booting from a system with outdated browsers. For example, many banks will refuse to allow you to log in if you are using an older version of Internet Explorer or Firefox. Your bootable flash drive can be using Firefox v50 instead of Firefox v3 (released in 2008). You can also use your bootable flash drive to provide you with an extra level of security. Since the flash drive doesn’t automatically write to your hard drive during use, then passwords, bookmarks and browser cache are not saved to your hard drive. Here are a couple of screenshots of a flash drive I used this afternoon.
If you’d like to try something similar on one of your computers, just bring me a flash drive and I’ll configure it as a live USB for just $35.