EBay calls it “sniping” and encourages it, since snipers lead to higher winning prices. No matter when the bid is placed, the highest bid wins.
There are many services which will snipe automatically in the final seconds of an auction, for those who like to sleep or work rather than watch their bids obsessively. EBay also encourages those.
To win you can place your bid at any time, just be sure it is your maximum bid. The usual mantra is “Bid once, bid your maximum, bid late.” ( The last of those is to prevent sketchey bidders who push up your bid with no intention of winning.)
