You store one spell that you can normally cast in a wooden quarterstaff. Only one such spell can be stored in a staff at a given time, and you cannot have more than one spellstaff at any given time. You can cast a spell stored within a staff just as though it were among those you had prepared, but it does not count against your normal allotment for a given day. You use up any applicable material components required to cast the spell when you store it in the spellstaff.
The staff that stores the spell.