Online Threat Alerts (OTA) - Alerting you to scams and frauds.
Scamming - Fraud
A buyer will claim to have sent you payment through PayPal for an item you have placed on Craigslist. You'll get a confirmation email, but it's bogus. If you log into your account directly at www.paypal.com, which you should always do, the payment will not be there. The seller will then claim it's an invisible transfer, which is something that does not exist on PayPal.
The scammers may also send a fake PayPal Payment Notification to you. If you click on the link in it, in an attempt to view the payment, you will be take to a fake PayPal website created by the scammers. And, if you attempt to sign into the fake website, your account credentials will be sent to the scammers.
So, before sending or shipping an item, always sign into your PayPal account directly instead of clicking on a link in an email message, to ensure that you have received your payment.