Classes of nebulae are emission nebulae, reflection nebulae, planetary nebulae, supernova remnants, and dark nebulae. Emission nebulae shine by internally produced light. They are often the birthplaces of stars. M42 in the sword of Orion is the best-known emission nebula and is visible to the naked eye as a cloudy patch. Binoculars and telescopes give very nice views of this wonderful object.
Reflection nebulae shine by reflecting light from nearby stars.
Most are very faint, but M78 in Orion is visible in any telescope. The star is often completely annihilated or leaves behind a small pulsar. The gaseous and plasma remnants slowly diffuse into space, becoming visible as twisted filaments or nebulous blobs. The most famous supernova remnant is the Crab Nebula in Taurus. Dark nebulae are regions of dust which obscure stars or bright nebulae behind them.