Types Of Races Held In Australia.

Races can vary depending on type, distance, type of horse entered, prize and weighing system.
Minimum Race Distance

The minimum distance horses travel in Australia is 800 Metres. Maximum lengths are determined by race and horse types.
Minimum Distance May Be Altered
At times, racing stewards may alter the distance of a race. If a race is less than 2,400 metres then it can only be altered up to 200 metres either way. If a race is more than 2,400 metres, then the maximum alteration is 400 metres.
Horse Racing Special Categories
Novice Races: for horses that have never raced before.
Maiden Races: for horses that have never won.
Auction Plates: for horses bought in public auction that are yearlings (weight allowances may be given in relation to purchase price).
Selling Races: in which the winning horse is auctioned afterwards.
Claiming Races: in which horses may be claimed for purchase at a specified selling price.
Horse Race Classes
A CLASS ONE RACE is one restricted to horses which, at the time of
starting, have not won more than one race on the flat.
A CLASS TWO RACE is one restricted to horses which, at the time of
starting, have not won more than two races on the flat.
A CLASS THREE RACE is one restricted to horses which, at the time of
starting, have not won more than three races on the flat.
A CLASS FOUR RACE is one restricted to horses which, at the time of
starting, have not won more than four races on the flat.
A CLASS FIVE RACE is one restricted to horses which, at the time of
starting, have not won more than five races on the flat.
A CLASS SIX RACE is one restricted to horses which, at the time of
starting, have not won more than six races on the flat.
All classes have provision that in determining the eligibility of any horse no account shall be taken of any wins in Class A, Class B or Trophy races, other than a win as a Maiden horse.
The Horses Age May Restrict

In flat racing, a race may be restricted to a certain age group; two year olds; three year olds; four year olds and older.
The Horses Sex
Some races are for horses of one sex only, or colts and geldings only.