The tax legislation is nearly 15,000 pages long and the answer to your question would be an essay. You could start here: the definitions at section 995-1 of the ITAA97:http://law.ato.gov.au/atolaw/view.htm?rank=find&act=pac%2F19970038%2F995-1~Income%20Tax%20Assessment%20Act%201997%20(38%20o f%201997)&criteria=AND~pac%2F19970038%2F995-1~provid~exact&target=pac/19970038/995-1&style=java&sdocid=PAC/19970038/995-1&recStart=1&PiT=99991231235958&recnum=1&tot=1&pn= ::

ac%2F19970038%2F995-1When you see an asterix * before a term or word it means it has a definition.You can also search those terms here:http://law.ato.gov.au/atolaw/search.htmBut restrict your search to Legislation.All of them are basically assessable income except for exempt income.