Deer/Elk areas are areas within a GMU that are established usually due to a prolonged damage issue or an overpopulation in a small area. So WDFW will create the areas so that they can issue special permits to hunt those areas so that the damage issues can be resolved. You can hunt the areas without having a special permit as long as the GMU that the deer/elk area is in is open under general rules.
The reason they do this is for example the 460 Snoqualmie GMU as a whole doesn't have a lot of elk, however there are a ton of elk within North Bend city limits and they are creating a lot of damage. So instead of WDFW issuing special permits for the entire 460 unit they issue permits just for the North Bend Elk area.