A vendor owes me a refund and asked what my PayPal account so they can send it to my Paypal. Do I give them my e-mail address that I sign in to PayPay????
A vendor does not need your email address to give you a refund. The vendor needs to go to the PayPal transactions and click on the refund option. A true refund must be associated with the payment transaction.
If the vendor wants to send you money as family/friends, then you provide the vendor with your PayPal email address. That would be a separate payment which is not associated with your original payment.
