Crampons stop your feet slipping on steep snow and ice, and can be loosely defined by the number of points they have.
'Instep' crampons are attached to the instep of your boot and are often called '4 points' even if they have more. They are fun and cruisey and great for messing around in. '6 points' are a bit more serious and are attached under the ball of the foot. ‘10 points’ are the full length of a boot and typically have 6 points under the ball of the foot and 4 under the heel. 12 points are similar, but have extra forward pointing spikes for serious climbing. Be careful not to gash your leg with these more full on crampons.
Cheaper crampons are often stamped out of a few pieces of metal, then welded together and bent to shape, whereas quality crampons are assembled from a lot of separate components. For most Australian purposes, either is fine.
If you have crampons that extend the full length of your foot, you should wear them with rigid boots as they are not designed to flex under the arch of the foot. If you don’t have fairly stiff boots, full length crampons can fall off, bend or break.