supply = passing drugs to another another person -whether or not for money. This includes passing on a pill to a friend, even if for nothing, passing the packed bong, etc.
trafficking = carrying on a business of drug selling - so commercial quanitities (which can be as low as one depending on the circs), making a profit, and organising drop-offs and pick-ups fall under this category.
possession - knowledge + control. In QLD it is assumed if drugs are found on your person, or in your house you both had knowledge and control of them, a presumption you have to rebut.
manufacture = create, purify, etc. So if washing chemicals (eg washing meth/mdma) be careful, this is pretty close to manufacturing in the eyes of the law. Also, having a heap of glasssware lying around doesn't look too good.
In answer to your Q - even if you only pass on one pill to someone, you are now their DEALER. There are no special numbers in place, or an unwritten drug code. If you get busted passing one or one thousand it's dealing.