The tab makes it possible to view on-screen hover-help for those running under Windows -- this feature will hopefully also be available in a future revision of Excel for the Mac.
Hover-help? Sure. Look:
Just let your little mouse cursor hover above the options on the Lertap tab, and a bit of help comes into view. Hover help. (The "view" is better on Windows versions of Excel -- the Mac version's hover help is a bit less helpful at the moment).
Page ahead to see what the Lertap tab's options do.