Description of a link

I would like to know where you can change the description of a page ( the text that comes up on mouseover )
( this is the site: https://195.22.100.240/~glenn/ )
its a little enhanced by the theme but this site has it too when u mousover

* Home
* About
* Extend
* Docs
* Blog
* Support
* Hosting
* Download

my english is not so good and thats probably why i can’t find it ??