Further more, you have already discovered that you can put in an upper bid amount, but might not necessarily have to pay it.
This acts as a way of protecting your own highest bid if you cannot get to the computer as often as you like, as others might come along, try to bid against you but give up after a while if they see they are not getting anywhere/ see the price rocketing.
You might see an item that you want more than anything else, and the starting price/ highest bid amount might be, for sake of argument, £100. So you bid the £100 but then also bid for a higher amount, say £200.
If £200 was the highest you were prepared to pay and you still get outbid, then good luck to the other bidder, but at the same time, the other bidder might only bid £199.99, so it is a ploy that can (and does) occasionally backfire!
So ONLY bid if you actually have the money, or faff about with low bids and hope that nobody else notices the auction.