Explaining every tag that exists would be too long...
Some tags are for general use, for example archon can be used in every post.
Some are community/subject related, for example photography can be used for every post related to...photography.
When you stake those "coins" in your wallet, for example archon, every time you vote on a post with that same tag, the author of the post get some archons. It works a bit like hive power, the more you have, the bigger your vote.
Of course, you are also free to sell those tokens for swap-hive and transfer those swap-hive back from hive-engine to the hive wallet...