Systemic functional grammar (SFG) is a form of grammatical description developed by Michael Halliday that views language as a network of systems used to make meaning. It is influenced by the work of linguists such as Saussure, Firth, and Whorf. SFG analyzes language according to three metafunctions - the ideational for construing experience, the interpersonal for enacting social relations, and the textual for organizing coherent texts. Grammatical systems like mood and process types play a role in construing different types of meanings associated with these metafunctions. SFG differs from theories like Chomsky's generative grammar by focusing on language use and meaning rather than grammatical rules.