Dark matter is a hypothetical form of matter that is inferred to account for discrepancies between the mass of visible matter and the gravitational effects observed in galaxies and galaxy clusters. Because it does not emit, absorb, or scatter detectable electromagnetic radiation, it cannot be observed directly through optical telescopes, leading to its designation as "dark." Its primary evidence comes from analyzing the rotational curves of galaxies and the dynamics of large-scale cosmic structures, which indicate that the gravitational forces require significantly more mass than what can be accounted for by visible stars, gas, and dust. While its exact composition remains unknown, theoretical physics suggests it consists of particles that interact only through gravity and possibly the weak nuclear force, representing a major component of the universe's total mass-energy density.