Universal Grammar is a theory in linguistics proposed by Noam Chomsky that suggests all human languages share a common underlying structure. This idea posits that the ability to learn language is innate to humans, meaning that children are born with an inherent understanding of grammatical principles, regardless of the specific language they are exposed to. According to this theory, the differences between languages arise from variations in the surface structure, while the deep structure remains consistent across cultures. Universal Grammar aims to explain how children can rapidly acquire complex language skills, often with limited input from their environment.