Perisher Blue is the largest ski resort in Australia. I is located in the Snowy Mountains, about 40km from the town of Jindabyne. It was formed about 5 or 6 years ago from the merging of the nearby Blue Cow/Guthega and Perisher Smiggins resorts (which formed from the seperate resorts of Mt Blue Cow, Guthega, Perisher Valley and Smiggins Holes.
It is certainly a large resort by Australian/New Zealand standards, and probably even by world standards. It has exactly 50 lifts, and, starting out as four different resorts, it covers a pretty large area of the Koszciusco National Park.
While it is possible to drive to Perisher, Smiggins or Guthega, many people prefer to park at Bullocks Flat below the snow line and catch the Skitube train through a tunnel in the mountain. This avoids having to use chains, drive on the icy road, start your car when it's covered in snow, etc.
While there are a few smaller resorts around, lots of people go to Perisher Blue these days. In the past, the smaller resorts would each have things going for and against them in terms of runs, quality of lifts and weather, making it a bit hard to choose sometimes. But Perisher Blue is now so big that there will be something for everyone. If one area of the resort is shitty, another might be OK.