The passcode is a 4 digit combination you choose when you sign up for the app. You can use your passcode, Face ID or Touch ID to open the app.
The PIN is a 4 digit combination you use when spending with your HyperJar card. For anything that costs £30 and under, you can also use contactless.
To be extra safe we advise you to have two different combinations for your passcode and your PIN.