Psionic characters fuel their abilities through a pool, or reserve, of power points. Your power point reserve is equal to your base power points gained from your class, bonus power points from a high key ability score (see section Abilities and Manifesters), and any additional bonus power points from sources such as your character race and feat selections.
If you have levels in more than one psionic class, you combine your power points from each class to make up your reserve. You can use these power points to manifest powers from any psionic class you have.
While you maintain a single reserve of power points from your class, race, and feat selections, you are still limited by the manifester level you have achieved with each power you know.