There are many types of nebula in this galaxy of ours! Here is a explaination of which nebula is which.
An Emission Nebula is a nebula that creates the most stars. They are filled with younger stars and brown dwarves and are arguably the prettiest nebulae. These nebulae on the galactic map are the dark red ones.
A reflection nebula is a nebula that reflects the light of stars in every direction making them oddly bright nebulae. These nebulae are the pink polygonal nebulae.
A dark nebula is a nebula so dense in dust that it covers light. These nebulas are arguably rather dangerous to transverse and asteroid fields are much more common in them than any other nebula thanks to the potential for unforseen threats... These nebula are the dark blue ones out lined in cyan.
A globular cluster is a netweork of stars near eachother. They vary in size, but the globular clusters here are the inbetween for open clusters and on the map it is the purple bowl shapped nebula icons.
An open cluster is a cluster bigger than a minute cluster, but smaller than a globular cluster. On the map it is the orange bowl shapped nebula icons.
Massive clusters are well, massive and contain large amounts of stars in them and remind us all how little we are in comparison to the universe. These clusters are the large green nebula icons on the map.
They the are very yellow nebula icons on the map that vaguely look like a reversed L. These nebula remain unclassified and seem to oddly enough be artificial. Nothing much is known about these.
Minute clusters contain only a small amount of stars in comparison to open clusters. These clusters are the blobish yellow green nebulae on the map.
Nebulas that are very explictly hybrids of the three nebula types known. These are very colorful and are the somehwat diamond shaped red nebulae on the galactic scale map.