Resource credits recharge over time.
They are consumed whenever you comment, post, vote, or interact with the HIVE blockchain.
The more HIVE Power you have, the more transactions you can undertake on the HIVE blockchain.
Let me know if you have further questions.
I have enough power, few activities that doesn’t warrant my resource credit to drain at all. My greatest surprise was seeing my downvote power drained when I didn’t downvote anyone.