Eckert (chapter 19) defines vernacular as the language that is the most closely associated with locally-based communities. The standard is the language that is used in ‘globalizing institutions,’ which include schools and universities, business and government offices, and banks. Both variants are used by people to show connection/membership either with local or wider (more general) community.
Wolfram (chapter 4) defines vernacular as a social dialect spoken by socially subordinate groups. He claims that this term is analogous in a certain way to the term vernacular language that refers to ‘local or native languages of common communication’ and is contrasted with the official standard language in a multilingual society. He continues to argue that ‘vernacular varieties are characterized by the presence of socially conspicuous and negatively valued structures’ (p. 60).
As we see, Eckert views vernacular in a more positive way. Through the use of vernacular languages their speakers can identify themselves with local groups thus achieving the sense of belonging.
Reference: Finegan, E. & Rickford, J.R. (Eds.), (2006) Language in the USA. Cambridge: Cambridge University Press.