Why might I want to use a clipboard manager?

I recently saw this poll asking for the "Best Linux Clipboard Manager". What actually is a clipboard manager and in what situations would a clipboard manager be useful?

Are there some differences in the default clipboard behaviour of Ubuntu to other (Windows or Mac) systems?

Persistence is probably the best selling point for me. Most CBMs allow you to store the same items across sessions (even platforms), mobile (if your profile is) and especially in the case of X-based applications, selected items* are remembered after the source application closes (something that is not natively true).

Multiple clipboards is something I don't use too much but it' very handy if you find yourself juggling several bits and bobs at once. You can do all your copying at once and then get on with whatever you're doing. Less back-and-forth.

These are both negatives if you regularly copy sensitive data as it could be a security issue.

* Just an explanation: you do know you effectively get two clipboards out the box? There's the traditional Control+C, Control+V clipboard but there's also something called "primary selection". Select some text and then middle click where you want it pasted. I find this very useful for quick, precise, multiple pasting.

I tried a clipboard manager once called Parcellite and now I cannot live without it.

A clipboard manager is one of those things that you never need until you try it and then without realising it, you can't work properly without it.

Not only is it really useful when editing code and config files ( because you can store more than one thing on the clipboard at a time meaning you can cut a bit here, copy a bit here, paste the second bit, then paste the first bit and so on ) but it is also really useful as a quick temporary storage.

I use it to store URLs, phone numbers, configuration snippets etc, whilst I am working on something.

If it is something I want to keep for a while I will paste it into Tomboy but a lot of information you need is only required for perhaps fifteen minutes, and it is as easy as hitting Ctrl+C and it is there, using notes or files is over kill for this ort of information. Normally you would have to rely on your memory, or I believe you can use sliced up tress to store information too.

It is a brain extension that means I don't have to remember things.