1. A map that does not fit the standards of the Hive. It may either be too simple, undeveloped, incomplete, have a poor description, or a multitude of other things. Usually the moderator will leave a comment on what you should fix.
2. Yes, just make the updates and make a post in Staff Contact saying that you have updated your map.
How to get it approved?
1. Look at the approved maps. Compare yours to theirs. If you think yours is really lacking, then it won't be approved. If you think yours measures up with the other approved maps decently, then it will probably be approved.