Ebay is many things:
an auction (price goes up as people bid) with a set end time/date,
an auction with a 'reserve' means the price will have to hit a certain price before the seller will sell it,
some are 'buy it now' (you pay the price posted),
some are 'buy it now or best offer' this is when you summit the price you want to pay and the seller will respond (accept, decline or counter-offer).

Some sellers/buyers try to trade outside ebay (say you offer a price on a rug (with a set price) and the seller says>I will sell it to you for less, send me a check or whatever, eBay is cut out of their profit and you risk being ripped off).

*you could ask the seller to notify you if they 'lower the price' or 'have a sale', but most of the time, this makes the seller know your interested and they sometimes will even relist it at a higher price...

I have found deals, but there is always a risk involved (will the package get lost/damaged in the mail, did the seller mislead, did you pay attention to the 'shipping price' and 'return policy'...I once returned an item and the seller did not refund my $ which means going through the ebay steps to getting a refund~time+headache)
I like eBay because I'm a thrill seeker/risk taker.