dark matter is a stand in, not a known type of particle. astronomers realized, that in galaxies there had to be way more mass than is visible due to the movement of stars within. but since it couldn’t be detected in any other way than through its gravitational influence, it was called dark matter.

this person has given the best answer so far. there is no thing we could identify as dark matter. the concept of it is more like a roadmap, a question to be answered.