what do sociolinguists mean by the term variety?

A variety is a set of linguistic forms used under specific social circumstances, with a distinctive social distribution.

* Formality increases between participants (speaker and hearer) when the social distance is greater. Informality (Solidarity) increases when the social distance is little between participants (speaker and hearer).

* Social status depends on a number of factors such as social rank, wealth, age, gender and so on; therefore the person with the higher social status has the choice of using formality or informality (solidarity) when addressing other persons of lower social status. But the person with the lower social status uses only formality when addressing a person of higher social status.