A site where one may bid on auctions for almost any item imaginable, (not just useless trinkets, as implied by the other definitions here), with the allure coming from the incredibly cheap prices of nearly everything that gets listed. Often, it is possible to find items listed at half their retail price. Granted, shipping costs are usually high, but an extra $5 on shipping doesn't overshadow paying $300 for a new graphics card that's being sold for $400+ everywhere else.
eBay is like life itself; there is a vast array of choices to suit every possible taste and desire, from furniture to video games, to electronics, to books and trinkets.
Fraud is generally not a problem, since there are thousands of well-known and trustworthy sellers, easily identifiable by their feedback records.
One of the great mysteries of life is the mentality of people who bid on auctions days before they end. Are they intentionally trying to drive the price up? Do they not realize that eBay is an auction site? Or are they so naive as to believe that others wanting to purchase the item will let their bids sit for days on end, without being outbid?
Even more mysterious are those individuals who choose to bid repeatedly and consecutively on particular items. What explanation there could possibly be for such irrational acts, I cannot even speculate...