The Overland Track leads through some very diverse wilderness environments. Each day is different from the last. Most people walk the track in 5-6 days, but you can walk it quicker or allow more time to really soak up all that is on offer.
Most people walk south, and during fee-based booking season this is a must walk north to south. Starting near Cradle Mountain and walking to Lake St Clair. There are campsites, huts and toilets every 10-15 kilometres. You'll find water tanks at each hut and plenty of creeks from which you can collect water (and treat it before drinking).
As well as getting a sense of each section of the walk, you will want to put together an itinerary. Here are some suggestions.