As a pilot, you cannot escape knowing this terminology. Knowing how your instruments do their measurements ("indicated vs true air speed", among others) is absolutely integral to the job, if you don't want to fly into a formation of "cumulo-granite" somewhere along the line.

One is what your pitot tube is telling you - which is a combination of altitude, weather conditions, wind, and airspeed.

The other is how much air is flowing over your wings - which is what actually keeps you aloft.

To quote the ace fighter pilot Yogi Berra - "In theory, theory and practice are the same. In practice, they are not".

You cannot escape pressure-altitude. It has way more implications than this. Starting with your ability to get off the ground.