Parce que

The cause introduced by parce que is not obvious to the listener and requires an explanation.

• Il reste à la maison parce qu'il est malade. (He stays at home because he is sick.)
• Je prends le bus parce que ma voiture est en panne. (I take the bus because my car is broken down.)
• Nous avons annulé le voyage parce qu'il pleuvait. (We canceled the trip because it was raining.)

In these examples, parce que introduces an explanation.

Puisque

Puisque introduces a cause known to everyone or considered obvious by the speaker and listener. It is often used to remind a fact already accepted or obvious to justify an action or conclusion.

• Puisque tu es végétarien, je te conseille de choisir le plat avec du tofu. (Since you are a vegetarian, I advise you to choose the dish with tofu.)
• Puisque tout le monde est d'accord, nous pouvons signer le contrat de vente. (Since everyone agrees, we can sign the sales contract.)
• Puisque tu n'aimes pas le café, je te ferai du thé. (Since you don't like coffee, I'll make you some tea.)