Spell Slot

Spell Slots are needed in order to cast or maintain spells, with each spell you cast or maintain occupying a single Spell Slot (by default, although this can sometimes vary). Fleeting or Reflex spells occupy the slot only until the end of the turn in which they are cast, while Maintainable or Enduring spells fill the slot for as long as they are maintained – with the slot becoming usable as soon as the spell ends (although like Fleeting spells they occupy the slot at least until the end of the turn in which they are cast, even if they are dropped immediately after casting). By default the number of Spell Slots you have is equal to your Concentration.