For example, I was a manager of a call center for an undisclosed company (a major ISP) once and was instructed to micro manage the employees from the higher ups. I didn't enjoy it very much but everything was tracked from the time spent on the phone, the hold times, and even how long you were signed out of the phone for a restroom break. When or if the numbers dipped below average, you'd be put onto a plan to improve or let go.
I would say that making sure that your employees arrive on time, making sure they don't spend all day hiding in the loo, or standing outside smoking etc is just managing, not micromanaging.
in my thoughts, micromanaging is as said above, constantly looking over someone shoulder telling them how to do their job.
when my boss starts telling me I'm constantly late back from lunch and need to improve, that's fine, he's doing his job.
when he starts looking over my shoulder and telling me how I should be doing my job, that's when problems start.