What words refer to the type of language a person speaks?

dialect, foreign language, accent, pidgin, slang, colloquial,

What words refer to the language used to talk about a particular subject?

terminology, jargon, specialized vocabulary, technical terms,

What words are used to talk about language?

linguistics, linguistic, metalanguage, vocabulary, dictionary, grammar, syntax, morphology, phonology, phonetics, sounds, semantics, meaning, pragmatics, rhetoric, pronunciation