מה ההבדל בין פנים ובין פרצוף?

Sehen Sie eine Übersetzung

No difference. You may use them interchangeably in most contextes, but still each of them has a slightly different connotaion. While פנים (panim) is usually used when speaking of or describing neutral to nice-looking face, פרצוף (partsUf) has a slightly worse connotaion, and used to describe a neutral to ugly face.

However, you should remember that it isn't a rule of thumb.

Examples:
איזה פנים יפות = what a beautiful face
But you can't say:
איזה פרצוף יפה

You can say both: (ugly face)
פנים מכוערות
פרצוף מכוער

Also here:
הוא טרק לי את הדלת בפרצוף/בפנים
He slammed the door right in my face

When you talk about the details in someone's face it will be פנים
יש לה צלקת על הפנים
She has a scar on her face

May there are more exclusions, so I'll add them if I remember.