Final answer:
Nebulas come from an area of the universe known as the interstellar medium (ISM). Interstellar material is concentrated into giant clouds called nebulae, which can be seen glowing or reflecting visible light.
Step-by-step explanation:
Astronomers refer to all the material between stars as interstellar matter; the entire collection of interstellar matter is called the interstellar medium (ISM).
Some interstellar material is concentrated into giant clouds, each of which is known as a nebula. The best-known nebulae are the ones that we can see glowing or reflecting visible light. These nebulae are formation regions for stars and planets.