V75 is the most popular Swedish betting form for trotting. To win you must pick the 5,6 or 7 winning horses. If no one picks all the winners or the payout on 5 or 6 winners is below 15 SEK, the winning pot (for e.g. 6 winners) is transferred to the next Saturday and the added to the winning pot for 7 winners.
If your horse is a non-runner, you will get a reserve horse instead. Either automatically or you could chose it.