Your booking reference. Your confirmation email includes it and a QR code.
Just your booking reference. Your confirmation email includes it, along with a QR code to show at reception so the campsite can bring your booking up quickly.
No printout needed; showing the email on your phone is fine. If you can't find the email, the campsite can also look you up by name.
Email support@pillowcase.io with your campsite name or booking reference and we'll pick it up from there.