String theory is a theoretical framework that proposes that the fundamental constituents of the Universe are tiny vibrating strings rather than point-like particles. Different vibration modes of these strings correspond to the various particles observed in nature. The theory attempts to unify quantum mechanics and general relativity within a single mathematical description. In many versions of the theory, additional spatial dimensions are required beyond the familiar three dimensions of space. These extra dimensions are thought to be compactified into extremely small geometric structures. String theory also predicts the existence of gravitons, hypothetical particles that would mediate gravity. Although mathematically powerful, the theory has not yet been confirmed experimentally. It remains an active area of research in theoretical physics.