The Matthew passage conveys a downright opposite message to that of Orgon. It means that Tartuffe's piety is a spectacle, a theater show for Orgon and the masses to see. Tartuffe pompously prayed in church before the congregation (and Orgon, of course), kissing the ground all the time, pathetically sighing and demonstrating his piety very loudly.
Think of it like this
Internal: A force inside yourself
External: A force outside of yourself
So if there an external force, it’s a force from outside so an example would be bullying. You wouldn’t want to go where you are being bullied so that would be an outside force affecting you.
It's very calming and super beautiful
The Climax is were you see the tensions at its peak.