So you’re switching to Linux because you’ve heard it’s a great way to revive an old PC, but after checking out various Linux operating systems (also known as distributions or “distros”), you’ve discovered that your hardware is still too slow. Unless, that is, you install something like Xfce.
That’s great. There’s just one problem: what does that even mean?
A desktop environment is what you see on your computer screen. It’s the panels that hold your applications, notifications, and the time. It’s how you open applications and switch between them. Ubuntu, Mint, Manjaro and many other Linux distros offer a Xfce desktop option.
Find out more about Xfce at http://www.makeuseof.com/tag/xfce-explained-linux-speediest-desktop/ 
Xfce Explained: A Look at One of Linux’s Speediest Desktops
If you’ve recently switched to Linux and are finding things a bit slow going, you probably need a lighter desktop environment. One good option is Xfce.