Craigs list is a person-to-person sales site.  Most often the payment is in cash and the exchange happens in a parking lot located near the homes of the buyer and the seller.

Scammers have found Craigs List, too.  The way the scam works, they offer to buy an item without ever having seen it.  They want to pay by cashier's check.  The cashiers check includes some extra money that the seller is to wire a shipping firm selected by the buyer.   The seller deposits the check in his bank, then wires the shipping fee to the shipping company.  Wired money clears instantly.  The cashier's check is a well-made fake and bounces a couple of weeks later.  The seller has to pay the bank the entire amount of the check, including the shipping fee, plus an extra fee for depositing a bad check.  The buyer and the shipping company share the shipping fee.