A Vegemite sandwich to an Australian kid is the equivalent of a peanut butter and jelly sandwich to an American kid - but the taste is QUITE different!
Vegemite is one of several yeast extract spreads sold in Australia. It is made from leftover brewers' yeast extract (a by-product of beer manufacture) and various vegetable and spice additives. It is very dark reddish-brown, almost black, in color, and one of the richest sources known of Vitamin B. It's thick like peanut butter, it's very salty, and it tastes like - well let's just say that it is an acquired taste!
Australian children are brought up on Vegemite from the time they're babies. It is said that Australians are known to travel all over the world with at least one small jar of Vegemite in their luggage, for fear that they will not be able to find it.