Note: The following text is taken from the What’s New part of the PC Study Bible startup desktop.
By 'hover' we mean the ability to hold your mouse cursor over an item and have something 'pop-up.' This is similar to holding your mouse cursor over a button to view a pop-up description of that button. However, the new 'hover' capability is specifically for items in reference lists (for example, in concordance and Global search results, in topical works like Nave's, and in The Treasury of Scripture Knowledge).
It enables you to move through a list of items and quickly view a 'snapshot' of each item of interest, without having to double-click on each one. As always, when you find one of interest you can double-click on it to display it in the secondary panel and continue your study from there.
Prior to version 4.2G, use of the Hover feature would drive your CPU usage to 100%. See KB691.