It refers to the space between stars, including:

* The vast emptiness between stellar systems.

* The gas and dust that exists in the interstellar medium.

* Objects like planets, asteroids, comets, and interstellar gas clouds that travel through this space.

The term is often used to describe things that:

* Originate in or travel between stars. This includes interstellar travel, interstellar gas clouds, and interstellar dust.

* Are related to the space between stars. This includes studies of the interstellar medium, the search for extrasolar planets, and the potential for life on other planets.

Here are some examples of how "interstellar" is used:

* "The spacecraft embarked on an interstellar mission to explore distant galaxies."

* "The interstellar medium is filled with gas and dust that can obscure our view of the universe."

* "Scientists are studying the composition of interstellar dust to learn more about the formation of stars and planets."

Overall, "interstellar" signifies something that is located, occurs, or is related to the space between stars.