Do we know what '~' is for?

We have been using our computer keyboard for a long time. But are we using all the keys? Obviously not. Because it is not required.

Ok, at least do we know the functions of the rarely or unused keys? Certainly not!

For example we rarely use function keys that are numbered as F1 to F12. We do not use '^' also.
Do we know what '~' is for? When did it start appearing on our keyboard?

Here is some useful information about a file with '~' that appear on our desktop.

To say it in brief:
"This file started appearing on people's desktop after the April 2003, Cumulative Patch for Outlook Express (330994) update released by Microsoft. If that update is installed and you take any action that changes the Windows Address Book the tilde file will appear on your desktop."

However, you can click on the link above to know in detail.