What does that mean
When browsing the site you will notice some words have are highlighted in red and when you pass the cursor over them they will give an explanation.
This is done by using Creative Minds Tooltip Glossary plugin.
Installing and Setting up your A-Z WordPress glossary is easy. The plug-in allows you to add Terms to the Glossary which will then be highlighted on every post or page of your site. Once the Plugin is enabled, users can hover over the term, word or phrase and a tooltip window will appear upon hover over, displaying the term definition. An A-Z Glossary index page and a term page will be created for each term that is added. While the index page contains all the referenced keywords or phrases, the term page includes the corresponding term definitions and displays a list of links that connect back to the source page, where the highlighted word or phrase appears.