How to bid or buy

[aang8884]

When I place a bid on eBay, I often find that - before my bid is posted - another bid is entered that is higher than my bid.

How can someone / something (eg: computuer) place a bid greater than mine BEFORE my bid is posted??!!

(a) Is this the seller automatically attempting to pump up bids to his/her "reserve" price?

(b) Is this another bidder who has somehow placed an "automatic" bid increase on an item up to some threshold limit they are willing to pay?

(c) Or is this something else causing this behavior??

Thanks in advance