The trick with vegemite is to remember that it is going to be salty - very salty. And to spread it really thinly on the toast.

Rissoles are sorta like meatballs. Lamingtons are basically stale cake covered in coconut.
And cordial in this instance is really strong flavoured sweet stuff that is supposed to be watered down. REALLY watered down. And lots of Americans try drinking it straight and then wonder how Aussies can possibly enjoy something that is so sickly sweet. It's the standard drink for kids' birthday parties.
I think most of the other food I've mentioned is reasonably self explanatory...

(love your icon, by the way)