Australian English is similar in many respects to British English, but there are a few cases were Australian English is closer to American English. For example: Australian English uses the American English truck instead of the British English lorry and the American English freeway instead of British English motorway.
Another area where Australian English is closer to American English than British English is with singular collective nouns: British English tends to use plural verbs with these, e.g. "The Government are committed". To an Australian (or American) ear this sounds quite odd.
With foodstuffs Australian English tends to be more closely related to the British vocabulary, eg. biscuit for the American cookie. However in a few cases such as zucchini and eggplant Australian English uses the same terms as the Americans, whereas the British use the equivalent French terms courgette and aubergine. This is possibly due to a fashion that emerged in mid-19th Century Britain of adopting French nouns for foodstuffs, and hence the usage changed in Britain while the original terms were preserved in the (ex-)colonies. Australia, for some uncertain reason, also uses the botanical name capsicum for what both British and Americans would call (red or green) peppers.
Australian English also incorporates several uniquely Australian terms, such as outback to refer to remote regional areas, walkabout to refer to a long journey of uncertain length and bush to refer to native forested areas, but also to regional areas as well. Many of these terms have been incorporated into British English through their adoption via popular culture and family links.
Some elements of Aboriginal languages have been incorporated into Australian English, mainly as names for the indigenous flora and fauna, as well as extensive borrowings for place names. Beyond that, very few have been adopted into the wider language.
Some regional variation in vocabulary and pronunciation exists, but such variations are comparatively small compared to the many regional variations of British and American English, and have only attracted academic and popular attention relatively recently.
Indeed, many Americans struggle to distinguish Australian English from New Zealand English, despite the difference being obvious to residents of both countries.