Hi Megha,
The letter ”A” in the part number means “absolute” so the pressure applied to P1 is measured against the vacuum reference sealed on the P2 side:

Our differential pressure sensors can be identified by a letter “D” in the part number (e.g. MPX5100DP) and two input ports:


Please take a closer look at this article to get a better idea about pressure measurement and level of integration of NXP pressure sensors.
Best regards,
Tomas