If you don't know what you're drinking, it's probably dark roast. Dark roast is like charcoal compared to light roast.

The coffee most folks use (i.e. Folgers, Maxwell House) is low-quality coffee made in haste to keep the price low enough for folks to be willing to buy it. They only offer darker roasts because disguise the inferior nature of the beans, or rather the inferior process. The unfortunate truth is that good coffee costs more to process because it takes longer to process and most folks don't want to spend that much on coffee. So, you get what you pay for.