Interstellar dust refers to tiny particles of solid matter that exist in the space between stars in a galaxy. These particles are made up of various materials such as silicates, carbon, and ice, and are believed to play a crucial role in the formation of stars and planets. Interstellar dust can scatter and absorb light, affecting the appearance of astronomical objects and influencing the chemical composition of the interstellar medium. Researchers study interstellar dust to better understand its properties and its impact on the universe.