Dark matter is very much real. We can detect its influence on nearby stars but cannot directly see or probe its nature.
More than 80% of the total matter in the universe is dark matter! The rest is made out of “dark energy” near 15%. Ordinary mass composed of stars like our sun and planets like the earth only takes up 4% of the matter!
There are many experiments that are ongoing trying to detect what exactly is dark matter and dark energy. So far, we know very little about them.