Answer:
The interstellar medium is the content of matter and energy that exists between stars within a galaxy.
In this sense, two components can be distinguished in the interstellar medium: dust particles and gas.
Dust represents 1% of the interstellar medium in mass, while the gas (consisting mainly of hydrogen and helium) represents 99% of the mass of the interstellar medium.
It should be noted that the interstellar matter is not uniformly distributed but is concentrated in molecular clouds.
