A topic summary which can be viewed from linked pages via a mouse rollover tooltip.
This is a feature of FlexWiki. Each topic can have a Summary attribute, usually placed at the top of the topic page. Once the Summary attribute is set, mouse rollovers of links to this page (on other pages) display the summary in a tooltip.
It's nice because it gives you an idea of what the topic is about before you click on it. In some cases it save you from clicking on the topic. In my own wiki I have many topics that are just a summary; acts like a dictionary and doesn't require any clicking.
So a topic called Ernex might contain this text:
Summary: A division of Moneris Solutions specializing in stored value and loyalty card programs.
Then any links to Ernex from other pages would allow me to see the summary text (the text after the colon) through a tooltip when I put the mouse over it.