When you place an item for auction on eBay, you (the seller) have the option of allowing bidders to keep their identity secret from other bidders. I don't really know why this matters and I never bother with it.
There is some sort of automated bot or something you can use to place an automatic bid in the final seconds. I once saw a link to it on the Moneysaving Expert website, although I've never used it myself. And some people just do this in person by watching during the final minutes of the auction. It cuts down the risk, to the buyer, of pushing the price up higher by declaring your interest early and thus inviting others to outbid you, but (unless you're doing it via an automatic system) it increases the risk of your forgetting all about it and missing the sale.