Systemic functional Grammar

I have had, not unlike all of my other classmates except for Mike maybe, have had a problem with what systemic functional Grammar is really about.
So, I have been doing a lot of reading (listen in my case) on what systemic functional Grammar is. Systemic functional Grammar is concerned with the choices that are made available in grammar for the speaker. It is concerned with the contextual practical uses to which grammar is put. This makes it very different from formal grammar which focuses on Word class verbs, nouns, adjectives etc the choices that are available to speakers and writers make the grammars concrete and steadfast, in other words, they are unbelievable. The meta-functional systems of this kind of grammar and include phrenology, the syntax, and Lexus. It attempts to encompass all areas of language. For example, it considers many aspects of the persona, such as the use of language used in

nicknames

which would denote how close the speaker is to the listener showing the interpersonal meta-functions of the social arena. It takes into account the relative social status and social standing and social distance all relative to only spoken texts.

Bibliography are asleep
Halliday, M.A.K. Introduction to functional grammar, 2nd ed. (1994) London: Edward Arnold.
O’Halloran, K.A. (ed.) English grammar in context, Book 2: Getting inside English (2006), The Open University,