Halliday and Dore (Simplistic explanations)

Instrumental 

Fulfills the speakers needs

Regulatory

Infulences the behaviour of others

Interactional

Develops social relations

Personal 

Used to convey their personal identity

Informative

Communicates information

Heuristic 

Learn about and exploration of the environment through language.

Imaginative

Explores imagination 

Labelling

Naming or identifying

Repeating

Echoing an adult

Answering

Direct response to another speakers utterance

Requesting Action

Demands

Calling

Attracting attention, normally through shouting

Greeting

Literal greetings

Protesting

Objections

Practising

using language when no one is around to practice