String theory is a theoretical framework that suggests fundamental particles are not point-like but tiny vibrating strings. These strings have different vibrational patterns, which give rise to the variety of particles in the universe. String theory also posits extra dimensions of space, beyond the familiar three, that are compactified at small scales. It aims to unify gravity with the other fundamental forces of nature, such as electromagnetism and the strong and weak nuclear forces. However, string theory is still a subject of active research and lacks direct experimental confirmation.