Each zone is comprised of an entire map. The map you see when you click “quest” is one zone. For example, the first zone you see in Bit Heroes is Bit Valley.
Each zone contains 12 nodes of which, every 4th node is a dungeon which you are able to play repeatedly.
Most players refer to nodes as flags and that is the common terminology when talking about them in world chat.
There are a total of 3 main repeatable dungeons in each zone with a special secret that unlocks after you’ve completed all three of those dungeons at each difficulty level. You earn a star when you complete a difficulty level for the first time.