Well that can be answered quite simply, he was the jockey on board Archer, winner of the first two Melbourne Cups. The real question though is who is the man himself?
John Cutts will forever be remembered in history as the first jockey to win the Melbourne Cup, but what the record books don't mention is the heritage of the man. There is evidence to suggest Johnny Cutts was also the first Aboriginal jockey to win the Melbourne Cup.
The story to suggest he has Aboriginal heritage is that during the Goldrush in the 1850's, many of the white stockman in the Riverina area left for the Victorian goldfields. They were replaced by local Indigenous men, one of whom was said to be a young John Cutts, who was born in the Nowra region and was well known as a very talented horseman. Many of these Aboriginal Stockmen also doubled up as jockeys during the era and most were never actually recognised as Aboriginal despite their success. So it is quite possible the legend is true.
On the other hand there is evidence to suggest he was born John Dillon, in Sydney c1829 to English stock. He rode successfully around Sydney tracks during the 1850's and won races for trainers in Melbourne in 1851 and 1852. He died in 1872 at the tender age of 43, only 3 months before Archer, the horse with whom his name is indelibly linked.
Interestingly whoever wrote his biography on Wikipedia is certain John Cutts was a white man born in Sydney, but offers no concrete evidence to support this, other than an apparent photograph of him with his wife,(who was actually the widow of his first training master William Cutts) which they say proves he is not Aboriginal. I tend to be of the opinion that any babies born in that era to English stock would have been properly recorded, as the population back then was quite small. The fact biographical records of Johnny Cutts show his birth as circa 1829 clouds the issue. I find it odd that he would take on the surname of his new wife over his own supposed family name of Dillon, unless he was for some reason trying to hide his family name. Also surely any photos from the 1860's would have to be inconclusive, particularly if he had mixed parents.
We now know the original legend of Archer walking from Nowra to Melbourne for the first Cup has proven to be false, and that he actually took the steamship from Sydney, after racing in Maitland immediately before the Cup. Maybe the legend of Johnny Cutts being the first Indigenous jockey to win the Cup also is false. What we do know is the first officially recorded Aboriginal jockey to win the Melbourne Cup was Frank Reys aboard Gala Supreme in 1973, an interesting tale in itself, but his is a story for another day.