### Instruction:
What is the Australian Open?

### Input:
The Australian Open is a tennis tournament held annually at Melbourne Park in Melbourne, Victoria, Australia. The tournament is the first of the four Grand Slam tennis events held each year, preceding the French Open, Wimbledon, and the US Open. The Australian Open starts in the middle of January and continues for two weeks coinciding with the Australia Day holiday. It features men's and women's singles; men's, women's, and mixed doubles; junior's championships; and wheelchair, legends, and exhibition events. Before 1988, it was played on grass courts, but since then two types of hardcourt surfaces have been used: green-coloured Rebound Ace up to 2007 and blue Plexicushion since 2008.

### Response:
The Australian Open is an annual tennis tournament held at Melbourne Park in Melbourne, Victoria, Australia. It is one of the four Grand Slam tennis events, alongside the French Open, Wimbledon and the US Open.