This time however you may be informed of a 'purchase' that you have recently 'made'.
When you click that link it will bring you to a phishing site that looks familiar to you. It looks the same as the real PayPal site that you visited all these while. You login and by then your account have been compromised.
If all that is too technical, then the easiest thing you can do is
1. DO NOT CLICK on such links.
2. Go to WWW.PAYPAL.COM directly and verify if you have indeed made such purchases.