The king of whiskys, Scotch is a famously complex topic that has been the subject of enough books to fill a few dozen libraries. Do not let that stop you from diving in and experiencing some of the most revered spirits in the world, though. There are only a few things that you need to keep in mind when looking at everything Scotland has to offer.
First up, there are two major categories to consider: blends and single malts/single grains. There is a long history of debate over a lot of the finer distinctions in Scotch whisky (spelled without the "e"), but you do not need to get too deep into the weeds on those distinctions to enjoy a good Scotch. In short, Scotch has to come from Scotland, it has to be aged in charred oak barrels for at least three years, it is distilled either entirely or primarily from malted barley, and most Scotches have a distinct peat-smoke character. Some are blended from whiskys made in different distilleries, some are from only one location. Neither style is inherently better or worse than the others; rather, the variety of Scotches is testament to their robust tradition of distilling. Blends can give you a great sense of what Scotch can be and the single malts can guide you to what suits your unique tastes.
When it comes to single malt Scotches, it helps to think if it like this: the terms "single" and "malt" are separate terms. "Single" means that all of the whisky in the bottle came from a single distillery, and "malt" means that it all came from malted barley and no other cereal grain. From there, you run into the issue of regions. Here is a brief run-down of Scotland's major whiskey regions (and this is the subject of some major debates):
Highlands—the largest of the regions geographically and still includes distilleries on the Hebrides. Mainland highland Scotches tend to be slightly lighter than Islays and often feature different cask finsihes for added complexity.
Lowlands—the southernmost region, and one of the smallest. These whiskys tend to be light, floral, and easy-drinking.
Campbeltown—the smallest of the regions, currently only home to three distilleries.
Speyside—home to the most distilleries, Speysides tend to be slightly more peat-focused than the highland whiskys, but still less peaty on average than the Islays.
Islay—pronounced like "EYE-luh," this region tends to emphasize the peat and often has a slightly briney or sea-air quality to the whisky.
Scotch is a fascinating and complicated field and well worth exploring. Of course, there are exceptions to every rule and each distillery does something unique. It is unfair to paint entire regions with a broad brush, but some generalities can help narrow down the options to guide you towards a new favorite.