Another name for the interstellar matter that will eventually form a star is a protostar or nebula. It is defined as a cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against other luminous matter. It is an interstellar cloud of dust, hydrogen, helium and other ionized gases.
Nebula is basically a cloud of gases and dust which will come together to make a protostar and eventually a star. These can be seen in the sky from a dark location as well. Example: Orion Nebula.
