eBay does not use an English Outcry auction format (bid and counterbid, going going gone to the last bidder at the full amount of the last bid) and you put yourself at a big disadvantage if you try to bid like it was such a format. eBay's auctions use a fixed-time semi-sealed-bid modified second-price (Vickery) format. This makes them fair to all potential bidders no matter their timezone or schedule. What you need to know to understand how eBay (this does not include "Live Auctions" on the eBay site which have different rules) auctions work:
The highest bidder (as of the end of the auction) wins, regardless of when his bid is placed (even if it was received in the last second and didn't show on your screen when your countdown got to 0), but the price is set by the SECOND highest bidder (generally that underbidder's highest bid plus 1 bid increment; less if the winner's bid is not a full increment higher than the underbid, including an earlier tie; more if needed to meet the reserve in a reserve listing; the starting bid amount set by the seller if there is only 1 bidder and no reserve).
During the auction eBay calculates and posts a "current bid", which is simply what the price will be if there is no further bid activity before the auction ends, and uses that "current bid" to set a minimum amount for new bids (1 increment over the "current bid" except for the very first bid, which need only be at least the "starting bid" amount set by the seller).
During and after the auction, eBay hides the full amount of the leader's/winner's bid to the extent that it exceeds that calculated price. (If the winner/leader has made multiple bids, only those that exceed the price have their full amount hidden.) For any such hidden bid amount, eBay substitutes the calculated price amount for the full amount of the bid.
When you bid less than what the current leader has bid before you (or the same amount--ties go to the earlier bid), you are immediately outbid and become the new underbidder and the "current bid" is recalculated at 1 increment higher than your bid (or the full amount of the previously hidden maximum if less than an increment over your new bid, including an earlier-placed tie). When you bid more than what current leader has bid before you, you take the lead at 1 bid increment over his/her (previously hidden) maximum (or the full amount of your bid if it is less than a full increment over his previously hidden maximum; but if it was "Reserve not met" before you bid and your bid was at least as high as the previously unmet reserve price you take the lead at the exact amount of the reserve price unless the general rule would dictate a higher price because the previously hidden maximum was less than an increment below the reserve).
Some people, including eBay, try to simplify this by drawing an analogy to an outcry auction, but one where eBay "automatically places bids on your behalf" up to your maximum bid (hence the phrase "automatic bidding"). This is an imperfect analogy, and in many cases people trying to apply it to a particular situation end up either oversimplifying or overcomplicating the process leading to many misconceptions. If you want to understand how the eBay bidding process happens you need to get away from that analogy. (It is not necessary to understand it if you know and use the following winning strategy below and are willing to accept the results as accurate even though you don't understand how they were arrived at.)
The only winning strategy on an eBay auction is to bid your real honest wouldn't-bid-an-increment-more TRUE maximum that you would pay for this particular item WITHOUT REGARD to what anyone else appears or doesn't appear to have bid. Since what anyone else has or will have bid by the time the auction ends is already figured into the price if you win, there is no need to try to figure it into your bid (other than to assume that someone else is likely to bid about the same amount as you, so it is a good tactic to bid a bit over the round number you likely have in mind as your true maximum to increase your odds of being on the winning side of what might have been a tie or a loss to someone who knows this tactic); all you need to figure is at what price point you would rather someone else get the item than you having to pay more. When you bid, early or late, or whether you put in a lesser bid(s) before your true maximum, those are tactical matters that may or may not influence the behavior of others (other bidders, potential bidders, and the seller) to your advantage or disadvantage.
