A curse is a negative and persistent psionic effect placed on another person. The specific workings of a curse depend on the specific ability, but most curses will persist with the target, remaining on them no matter how far they are from the psion that first placed it on them. To remain persistent in this way, most curses are composed of a certain amount of flux placed on the psion, 'attaching' itself to the target's mind in order to prevent itself from decaying away, essentially parasitizing the mental influence in a way similar to how flux can be controlled by a psion - except most people are helpless to curses.
A boon is simply a positive effect instead of a negative one.
Many curses only last a certain time until they naturally fade away, but some can last even indefinitely. Curses can be difficult to remove, an act called dispelling or exorcising. A psionic curse or boon can only be directly destroyed through the effects of order, otherwise abilities that dispel curses must transfer the curse in some way to another medium, 'bearing the burden' of the curse for the target. Examples of such abilities might include having to take on the curse for oneself, or having to destroy a metacreated construct of the curse in combat. Generally, the stronger a curse is, the more difficult it is to dispel, and it can be very especially difficult to dispel curses created from psions stronger than the psion trying to dispel it.
Awakening a Curse or Boon
Awakening with an ability involving a curse or boon is a good awakening option. Those who awaken in this way often awaken around an event fixated on a specific person - in the event of a curse, perhaps a desire for revenge or retribution, or in the case of a boon, a desire to protect someone close to you. Curses or boons created in this way have the potential to be fairly strong if they only occur once, due to the intense feelings an awakening event can cause. Curses and boons follow the standard ability application.