Sociolinguistic theory is the study of how language varies and changes in social contexts, emphasizing the relationships between language, culture, and society. It examines how factors such as region, class, ethnicity, and gender influence language use and perception, shedding light on the dynamics of communication within different communities. This theory plays a crucial role in understanding dialectal variations and the effects of social factors on language, as well as addressing issues surrounding endangered languages and efforts toward language preservation.