it depends what kind of plane you are flying, if you are flying a C172 as a commercial pilot, you would probably get only definitions from books. If you have to fly a plane that goes above FL250 you need to get a High Altitude endorsement, where you train for symptoms like hypoxia. (at least in USA)
some schools will provide a Hypoxia training, I did a training in a Medical center in Melbourne,FL where they put you in a chamber and simulates the loss of ambient pressure as you go up in altitude, and you get HYPOXIC. it was a really good experience