One of the ways that linguists think about language is through geographical distribution, commonly known as dialects. It's very easy to think about geography because of the wide range of locales in which English is spoken. Due to conquest and colonization, English is now a world language. There's British English, Australian English, and Nigerian English, among many others. In the continental U.S., most people readily identify a number of regional dialects: “Midwestern," "New England," "Southern." While some people might call them accents, linguists distinguish between dialect and accent. The term accent refers solely to the way words are pronounced while dialect includes pronunciation, word forms, vocabulary, and sentence structures.
Bramlett, Frank, "Y'all Better Ask Somebody" (2003). English Faculty Publications. 44.