While some of the screenshots won't be recognizable or meaningful to new StarCraft initiates, most of the action is generally recognizable (in a general sense) to a veteran RTS player. You can definitely get an overall sense of troops, constructed bases, and how the fight might progress if it were animated.
These new screenshots feature the Banelings, which sound like pretty fierce critters in their own right. Banelings -- a "morph" of the zergling -- are chemically volatile little buggers who spend their lives angry, temperamental, and ready to explode at any given time. Through tender loving care, Zerg Queens have been able to engineer the banelings in such a way that they'll explode exactly when needed. Presumably, "when needed" means "all over your troops." You can see the Baneling's idle animation on their feature page on the official site. They pump and undulate, and really do look like something that's over-filled and ready to pop given a moment's notice. Kind of gross, really.
Most of the details about Starcraft II will come "closer to release date," but it's still pretty tantalizing to get a first look at notable, trademark troops.
Gallery: Starcraft 2