A micro-bevel is simply a very small, secondary or tertiary bevel at the very edge of a blade. These are most often used when you want the majority of your bevel to have a specific look (such as a high polish) but still want the toothiness of working edge. 

Luckily, the process for creating a micro-bevel is fairly straightforward and easy to achieve on any edge. 

The first thing you'll want to do is to complete the process for sharpening your edge like normal. Find your angle and sweet spot and put whatever finish you'd like on your edge. Then, kick your angle out 4-5 degrees on both sides and switch to whichever stone you'd like for the edge. Most often you'll use a coarser grit, such as 600 or 800, to put the micro-serrations back on the edge. Do about 5 strokes on each side and you're good to go. 

Micro-bevels are great because you can also put a sharp edge on a blade quickly, without having to do a whole lot of work. For example, if you have a blade where the angle is changing drastically along the edge of the blade but you don't have the time to do a full reprofile, kick the angle out and put whatever working edge on you'd like. Then, when you have time, you can go back and do the real work to even everything out.