To show a tooltip with info (member info and Gravatar profile) when you mouseover/click on an avatar.
You can enable a tooltip that shows info about user/author when you rollover/click on related avatar.
Let's speak clearly: if you are loooking for a plugin that enables the standard Gravatar hovercards, this is not the plugin right for you. Please look for another one.
When you rollover/click on an avatar (e.g. of a comment author), a tooltip popups and shows:
The plugin comes with some filter hooks, so you can customise the tooltip content at all.
The plugin uses qTip plugin for jQuery.