A lowest unique bid auction is an auction where the winner places the lowest unique bid, rather than the highest bid as per traditional auctions. To enter you pay for each bid you place.
In the below example from Sweepola of a lowest unique bid auction, the winning bid is £5 because it is the lowest bid that no one else has also entered as a bid.
3 people bid £1
2 people bid £2
5 people bid £3
3 people bid £4
1 person bids £5 (unique & lowest) = WINNER
4 people bid £6
1 person bids £7 (unique but not the lowest)
2 people bid £8
8 people bid £9
1 person bids £10 (unique but not the lowest)
2 people bid £11
In this auction where the minimum bid is £5 we will look at the lowest bids placed.
Only 3 of them are unique: £5, £7 & £10
£5 is the lowest unique bid.
Therefore, the person who bid £5 wins