Question

What is the cloud of interstellar dust and gas that forms a star is known as?

Answer 1

(Star forming) Nebula.

Explanation:

Nebula could mean any astronomical object that looks cloudy and a source of diffused light. There are many cloud-like objects in space. Galaxies (spiral nebulae), Glowing shells of gas and dust ejected from the stellar interior towards the end of a Star's life (Planetary Nebulae), Supernovae debris (Crab Nebula etc). So it is better to explicitly state it as Star Forming Nebula. Orion Nebula, for example, is a star forming nebula.