"Phishing is an e-mail fraud method in which the perpetrator sends out legitimate-looking email in an attempt to gather personal and financial information from recipients. Typically, the messages appear to come from well known and trustworthy Web sites. Web sites that are frequently spoofed by phishers include PayPal, eBay, MSN, Yahoo, BestBuy, and America Online. A phishing expedition, like the fishing expedition it's named for, is a speculative venture: the phisher puts the lure hoping to fool at least a few of the prey that encounter the bait.
Phishers use a number of different social engineering and e-mail spoofing ploys to try to trick their victims. In one fairly typical case before the Federal Trade Commission (FTC), a 17-year-old male sent out messages purporting to be from America Online that said there had been a billing problem with recipients' AOL accounts. The perpetrator's e-mail used AOL logos and contained legitimate links. If recipients clicked on the "AOL Billing Center" link, however, they were taken to a spoofed AOL Web page that asked for personal information, including credit card numbers, personal identification numbers (PINs), social security numbers, banking numbers, and passwords. This information was used for identity theft."
Its when someone PMs you about giving them your account or tc/items in return for something too good to be true.