A clipboard manager is a program that retains a history of items you’ve copied or cut to your clipboard. Most operating systems only save the last thing you copied or cut by default. The clipboard manager allows you to review your clipboard history. Wikipedia gets into the details.
As someone who works with a lot of text, I find the clipboard manager to be an indispensable tool. For instance, when moving text around, the clipboard manager allows me to go back to a previous cut-and-paste and insert text where it should have gone, rather than where I put it.
In moving this site to WordPress, I spent a fair amount of time copying-and-pasting text and HTML. The ability to go back to previously copy-and-pasted snippets was a huge time-saver. I also find it tremendously helpful when I accidentally copy something over what I really wanted to keep in the buffer. This happens a lot when I Ctrl-C when I really wanted to Ctrl-V.
GNOME has a built-in clipboard manager, but there are lots of them for Linux. I’ve used Parcellite and Clipman and couldn’t tell you the difference between either of them, which is the beauty of the clipboard manager. As long as it can show you a history of things you’ve copied or cut, it’s working just fine. The interface is usually less important.
I’ll acknowledge that there are security risks with clipboard managers. If you copy-and-paste passwords, they’re in your history. Most clipboard managers allow you to selectively delete items if having a password existing in your clipboard history troubles you. If you share your user account with someone, it’s a legitimate concern. I also had a colleague who used a clipboard manager on what was essentially a public terminal, which is a pretty awful idea.
With that caveat, clipboard managers are wonderfully useful tools. It’s almost like a time machine for your cut or copied text. Anyone who works with words will quickly come to appreciate the ability to return to text that was worked with just a few copy or pastes ago.
If your desktop environment doesn’t already include a clipboard manager, there are a few options in your repository. The clipboard manager will quickly make itself indispensable to you.