Why does this taste bad?

To that info on grain charts that others posted, I'll add that there are differences among malters that are really worth trying to understand. And of course, everyone's taste buds are unique in their own right, so at some level, verbal descriptions of flavor must always fall short. I know of no good ways to learn these differences for yourself that do not involve tasting and brewing and tasting some more. That's part of what makes this a fun hobby! There recently have been some Basic Brewing podcasts and a Zymurgy article on approaches to learning different flavors from malts without necessarily going into the whole brewing process - you may find those helpful.