"Penetration" refers to moving your body towards the pit after takeoff. It's a term that's been used since the 1960s, when vaulters realized that if they don't "penetrate" (keep moving forwards), they're going to stall out.
Today, a more common term is to "roll the pole to vertical". I never heard that term until a few years ago, but it essentially refers to the same action. Either way ... since you're holding onto the pole ... the same action occurs ... to keep you from stalling out.
If you stall out ... or hit the bar on the way down (becuz you don't penetrate), you must correct your technique so that you DO penetrate (so that the pole DOES roll to vertical). Alternatively, you can lower your grip, or use a softer pole.
Or run faster and jump harder.
It's important that you land near the middle of the PLZ. If you don't, you're either not penetrating enough ... or you're blowing thru (penetrating too much).
Kirk