What is mini bump and what it does? And how?
As theymos describes it, it's simply posting in the thread. You don't reduce any of your bumping power by posting in a thread, but if it's the first time you've posted in that thread in the last 7 days 1% of your bumping power is directed towards the thread's bump score.
Mini bumps
If you haven't posted in a topic in the last 7 days, posting in it adds 1% of your base bump power to the topic's bump score. Deleted posts count against the 7-day limit, but not the topic's bump score.
Super bumps
Once per 24 hours, you can click a topic's bump link. When you do this, a modified bump power is calculated as your base bump power minus 15% for every super bump you've done in the last 30 days, and this is added to the topic's bump score. In other words, your modified bump power is base_power*0.85super_bumps_last_30_days.