First off, those categories are the regions in which the whisky is made. Now, there ARE some historical characteristics of those regions, but they are losing their prominence.
Highland: This is your "typical" scotch, as the big names in scotch (those found on menus everywhere) are nearly all Highlands. These would be Glenfiddich, Macallan, Glenlivet, etc... Speyside is a newly emerging region inside of "Highlands", but they are still Highlands.
Lowland: Auchentoshan is the most popular of the lowlands, and they exhibit the characteristic best known for a lowlander -- triple distilled. This is more like an Irish whisky, in that it is devoid of the rich malty flavoring of the double distilled whiskies in the rest of Scotland. Auchenstoshan's Three Wood, however, receives good marks, but the flavor is coming from the wood finishing, not the malt.
Islay: The big names in Islay are Ardbeg, Laphroaig and Lagavulin. These exhibit the big peaty taste (phenols) that Islays are expected to have. Bunnahabhain and Bruichladdich are non-traditional Islays. The Bunna is a "gentle" Islay, and the Bruichladdich could be anything. They are very experimental there...
Good luck on your studies. Congrats on the promotion.