While the study of sociolinguistics is very broad, there are a few fundamental concepts on which many sociolinguistic inquiries depend.
Speech community
Speech community is a concept in sociolinguistics that describes a distinct group of people who use language in a unique and mutually accepted way among themselves. This is sometimes referred to as a Sprechbund.
To be considered part of a speech community, one must have a communicative competence. That is, the speaker has the ability to use language in a way that is appropriate in the given situation. It is possible for a speaker to be communicatively competent in more than one language.
Speech communities can be members of a profession with a specialized jargon, distinct social groups like high school students or hip hop fans, or even tight-knit groups like families and friends. Members of speech communities will often develop slang or jargon to serve the group's special purposes and priorities.
Community of Practice allows for sociolinguistics to examine the relationship between socialization, competence, and identity. Since identity is a very complex structure, studying language socialization is a means to examine the micro-interactional level of practical activity (everyday activities). The learning of a language is greatly influenced by family but it is supported by the larger local surroundings, such as school, sports teams, or religion. Speech communities may exist within a larger community of practice.
High prestige and low prestige varieties
Crucial to sociolinguistic analysis is the concept of prestige; certain speech habits are assigned a positive or a negative value, which is then applied to the speaker. This can operate on many levels. It can be realised on the level of the individual sound/phoneme, as Labov discovered in investigating pronunciation of the post-vocalic /r/ in the North-Eastern USA, or on the macro scale of language choice, as realised in the various diglossia that exist throughout the world, where Swiss-German/High German is perhaps most well known. An important implication of the sociolinguistic theory is that speakers 'choose' a variety when making a speech act, whether consciously or subconsciously.
The terms acrolectal (high) and basilectal (low) are also used to distinguish between a more standard dialect and a dialect of less prestige.
Social network
Understanding language in society means that one also has to understand the social networks in which language is embedded. A social network is another way of describing a particular speech community in terms of relations between individual members in a community. A network could be loose or tight depending on how members interact with each other. For instance, an office or factory may be considered a tight community because all members interact with each other. A large course with 100+ students would be a looser community because students may only interact with the instructor and maybe 1-2 other students. A multiplex community is one in which members have multiple relationships with each other. For instance, in some neighborhoods, members may live on the same street, work for the same employer and even intermarry.
The looseness or tightness of a social network may affect speech patterns adopted by a speaker. For instance, Sylvie Dubois and Barbara Horvath found that speakers in one Cajun Louisiana community were more likely to pronounce English "th" [θ] as [t] (or [ð] as [d]) if they participated in a relatively dense social network (i.e. had strong local ties and interacted with many other speakers in the community), and less likely if their networks were looser (i.e. fewer local ties).
A social network may apply to the macro level of a country or a city, but also to the interpersonal level of neighborhoods or a single family. Recently, social networks have been formed by the Internet, through chat rooms, Facebook groups, organizations, and online dating services.