Microsteps are in-between positions that may only have fractional torque holding and going to the next step and varied accuracy in positioning. The 200 full steps are pretty much reliable, half steps are decent too.
Microstepping is for smoothness of operation. Take a big ratchet and give it 8 notches per turn and turn it fast. It's going to make a hell of a lot of noise and vibrate a ton. Take that same ratchet and give it 48 smaller notches and it will be much less noisy and feel smoother as it moves at the possible expense of the amount of torque it can hold against. It's easy to hear and feel the difference in a microstep driven motor and a full or half-step driven motor. But they may not actually move the table until a couple of microsteps are taken because they lack the full torque to move the load.
I microstep at 8 so 1600 steps per rotation and 5 rotations per inch or 8000 steps per inch, but I only count on the machine being able to position within 0.001". In most cases it *can* position to 0.0005" but there is no way in hell it's good to 0.000125" as the microsteps per would have you think.
ETA: I guess I missed the page 2 discussion before posting. I'll concur with the above. While I know I can get it to move 0.001" on command or very close to it. I can't get better than +/- 0.003 without going to some effort in how I approach the job. Use the whole table and it gets worse.
CNC: Making incorrect parts and breaking stuff, faster and with greater precision.