Hi Antares,
Some of my scientist colleagues are busy trying to map the dark matter in the universe.
It is called dark matter becuase it does not give off any light ..and it can't even reflect light from other stars and gases. So telescopes can not be used to see it.
But dark matter feels the force of gravity. Gravity is a basic force that makes matter attract other matter. Gravity holds you on your chair (the Earth's and your body's matter are attracted to each other) and makes things fall on the floor. (It also makes the Earth go around the Sun.)
So dark matter makes its presence known becuase it is attracting normal matter such as stars and nebula gases.
Hope this helps
Paulett