Urgent: BACs, Online Transfers and Plastic Money

To say I’m confused about the topic is an understatement. The more I’m trying to ‘get’ the concept, the more twisted this is all getting!
Aka I’d be extremely thankful if someone can tell me the difference between BACs and Internet/Online Transfers. I believe that using plastic money (Cr and Dr Cards, ATM cards etc) is considered as an online transfer, but does it also employ BACs?
And where does EFTPOS come into all this? Is eg a standing order an EFTPOS? If not, why not?
And when you have to pay via eg Cr Card at a retail shop, will *this* payment be labeled an online transfer or…? (BACs or EFTPOS)

So if anyone can give a try and un-weave this knot of confusion? Thank you! And I hope I don’t mess up any of your concepts with all this.