What do true nebulae, distinct from spiral nebulae, primarily consist of and where are they located?

Answer

Gas and dust clouds associated with star formation or stellar death, lying comparatively near in astronomical terms.

Objects remaining classified as true nebulae are associated with processes like star birth or death and reside within the relative proximity of our own galaxy, unlike external galaxies.

What do true nebulae, distinct from spiral nebulae, primarily consist of and where are they located?
HistorydiscoverySpaceastronomynebulas