Cross country skiing events come in many shapes and sizes, just like their participants. A good overview of different event types is provided on the DiscoverXC website. The majority of races in Australia are Mass Start Distance events, with a small number of Interval Start and Sprint events held as part of state and national championships.
All events are designated as Classic or Freestyle (also known as Skating). Again, Discover XC has a great section explaining the different techniques, but the basic rule is that skating (pushing off a gliding ski when it is not parallel with the other ski) is not permitted in a Classic event. When considering which events to participate in look for the (F) or (C) designation on the race calendar. Classic races have special parallel tracks groomed into the snow for the skis to follow. Freestyle races at most levels of competition in Australia will also have Classic tracks, with the exception of some championship events (usually Sprints) where it is expected that all participants will skate.