Australian English (AuE) is a variant of the English language, spoken mainly in the Australia.
Australian English began to diverge from British English shortly after Australia was settled in the late 18th century. It is similar to New Zealand English and bears some resemblance to certain dialects of South East England.
Generally speaking, Australian English spelling corresponds to British English spelling.
AuE makes a great deal of use of diminutives (e.g. arvo for afternoon, footy for football)
For a list of major differences between different kinds of English see Varieties of English Grammar and Varieties of English Vocabulary.