Micronized creatine is creatine monohydrate ground into finer particles. This makes it dissolve quickly in water or shakes and is often easier on the stomach than standard creatine powder.
Many people use it to help build muscle, increase strength, and improve power during lifting or sprinting. It also supports recovery from hard training sessions. A typical plan is either a loading phase of higher daily doses for 5 to 7 days, then switching to a steady maintenance dose, or just a consistent single dose every day from the start.
Mix it into any beverage and drink it whenever works best. Lots of people take it pre or post workout.