Dark matter is a fundamental concept in cosmology and particle astrophysics concerning a hypothetical form of matter that does not interact with electromagnetic radiation, thus making it undetectable by conventional means, but whose existence and distribution are inferred from its gravitational effects on visible matter, radiation, and the large-scale structure of the universe. This concept is central to explaining observed galactic rotation curves, gravitational lensing, and cosmic microwave background anisotropies, highlighting its critical role in the standard model of cosmology.