Racing: Guide to the Interdoms

What: Annual transtasman clash of the best harness horses, dating back to 1936. Separate series for pacers and trotters.

Where: Alexandra Park, Greenlane, Auckland.

When: Starts with five heats tonight, with second round on Tuesday and final round next Friday. Then two finals and two consolations on March 18.

How much: Total stakes of $1.7 million, with the pacing heats worth $40,000 each and trotting heats $30,000. Pacing Grand Final will be New Zealand's richest ever harness race at $750,000 and the trotters' final is a cool $250,000.

What's the difference: Pacers are slightly faster, with front and back legs on the same side moving in unison. They are helped to maintain that gait with leather straps called hopples.

Trotters move their right front leg and left back legs in unison, much like watching a baby crawl across the floor.

Who (pacing): The big pacing names from New Zealand are Elsu (winner of the last two Auckland Cups) and Just An Excuse (who beat Elsu in the last two New Zealand Cups). The Aussie assault, the biggest ever, is lead by Sokyola, who has won the last two Miracle Miles.

Who (trotting): The only two millionaire trotters to ever race in the Southern Hemisphere are here - stablemates Lyell Creek and Take A Moment. They are champions, but old champions. Their challengers include glamour mare Allegro Agitato, the Aussie with the unlikely name Sumthingaboutmaori and Delft who is one of the biggest trotters ever to race in NZ.

Humans: All the superstars will be there from New Zealand's greatest driver Tony Herlihy (The Iceman), Canterbury's renowned Butt brothers, Tim and Anthony, the all-conquering Purdon family. The Aussie dream team is headed by the King of the Interdominions Brian Hancock (five Grand Final wins), the mercurial Gavin Lang (three Grand Finals) and the most successful female driver in history, Kerryn Gath.

What can you win: Quite a bit. Over $10 million will be gambled during the carnival, meaning some big betting pools.

That will be jumpstarted by a guaranteed $1 million Pick6 tonight, for which you need to select the winners of the last six races. If you don't fancy picking your own horses you can get the computer to do it with an Easybet. And there are numerous on-course competitions, including giving away a SS Commodore.

Why does it matter: Money, for a start. Also transtasman skiting rights, which can affect our export markets to the US and how successful each country's yearling sales are. And if the winner of the pacing final is a stallion, the long-term payoff in the breeding barn could run into the millions.