Lets you add footnotes with qualifiers of you're choosing, then dynamically displays them when you hover over.
Activate like any plugin.
For those who have never done this, the easiest way is to login to your wordpress back-end, select the "plugins" section and select "add new". Then in the search box search for "jQuery Hover Footnotes". It should find and display it in a list. then just click "activate" and it should automatically download and activate it. Easy as pie.
Realize you can also download the plugin manually to your computer, and use the "upload" option on that plugin install page in your wordpress backend.