This is the follow-up to the Protoss tech tree that was exhibited at Blizzcon. Text comes from Gamespot.
Of course, basic units like the marine and the medic are back, though you’ll immediately notice the firebat is missing. Other units haven’t been completely removed so much as replaced by new, improved versions. The old goliath mech has given way to the new viking, which acts just like a goliath–until you research and enable its transformation ability, which turns it into a jet that can get it across otherwise impassable barriers. Another unit which has no respect for variable elevation is the reaper, which you hire from a bar with a female night elf dancing on top of it. These mercenaries build almost instantly, since you’re just hiring them instead of training them, and in addition to being able to jump up and down to higher and lower terrain, it can now throw a timed bomb and escape the area before it explodes. We saw a large group of these reapers all throw out bombs at the same time to do massive damage to an enemy base before beating a hasty retreat.
The terrans have quite a bit of air support in Starcraft II, at least as it stands right now. The predator is a new flyer that can only attack other aerial units, but it can also take on an intercept mode where it will attempt to shoot down incoming enemy fire (presumably things like missiles). Everyone’s favorite the battlecruiser is here again, but this time it won’t simply default to the incredibly powerful, single-shot Yamato cannon like it did in the first game. Sure, the Yamato is still here, but this time you’ll get to choose how to specialize each individual cruiser, between the Yamato and the new plasma turrets. The latter will produce a flurried cluster of beams that can decimate ground units, from what we saw of them.
Here's a couple of guides to help with your Starcraft - build orders, maps, units, tactics.