I would say that it's a phishing email. Check if it's in your eBay messages. If it's not, then it's a scam. If you clicked on the link or the attachment, update and run your virus scanner and malware programs. If you don't have any malware programs, download and run Malwarebytes Antimalware. Run a full scan. Change all your passwords (very important you do this).
Never ever click on links or attachments in any eBay or PayPal emails because phising emails look authentic. When you click on the link it will take you to a legitimate looking eBay/PayPal site. As soon as you put in your password, they can take over your account.
If you are ever unsure whether an eBay email is legitimate, check in your eBay messages.
