[dheera]

There are multiple types of nebulae. Absorption nebula (or dark nebula) and reflection nebula are clouds of "dust" (more likely lots of rocks).

There are also emission nebula which are clouds of ionized gases that emit light.

The horsehead nebula is an absorption nebula that sits in front of light-emitting emission nebula. It's fairly easy to image the horsehead with a star tracker and DSLR, though not to this level of detail.