On your paypal account go to your transaction details and click 'ALL SENT' it will then give you a list of things that have recently been paid through paypal. If you recognize the transaction then click DETAILS and it will tell you where and when and what item was purchased. If you can't find the transaction then click the filter 'PAYMENTS RECEIVED' and try and find the transaction. If you find the transaction then someone has either purchased something from you or you have received that payment as a gift.