Light Roast: Roasted for the least amount of time. Light roasts have the most caffeine (by volume) and the most acidity. The acidity in light roasts is often accompanied by a citrus or lemon tone which some people find pleasing to the palate.
Medium Roast: Slight more body than a light roast and less acidity. Medium roasts are the most popular and are considered to have balanced flavors. The acidity and body of a medium roast can vary but are usually somewhere in the middle.
Meduium Dark Roast: Roasted a little longer than the average medium roast. A richer fuller flavor with more body and less acidity.
Dark Roast: Sweeter flavors because the sugars in the coffee beans have time to caramelize. They have the least acidity and caffeine of all the coffee roasts and the longer roasting process gives it a richer flavor and full body resulting in a buttery finish. French roast is considered the darkest roast and has a smoky flavor.
Extra Dark Roast: Roasted a little longer than the average dark roast. Common flavors of extra dark roast coffee are often described as dark cocoa and brown spice with a smokey aftertaste.