Costs and Loci
Source Player Core pg. 298
Some spells require you to pay a cost or provide a locus. If the spell lists a cost, you must have the listed money, valuable materials, or other resources to cast the spell (such as gems or magical reagents), and they're expended during the casting.
A locus is an object that funnels or directs the magical energy of the spell but is not consumed in its casting. As part of Casting the Spell, you retrieve the locus (if necessary, and if you have a free hand), and you can put it away again if you so choose. Loci tend to be expensive, and you need to acquire them in advance to cast the spell, but they aren't expended like costs are. Unless noted otherwise, a locus has negligible Bulk.
A locus is an object that funnels or directs the magical energy of the spell but is not consumed in its casting. As part of Casting the Spell, you retrieve the locus (if necessary, and if you have a free hand), and you can put it away again if you so choose. Loci tend to be expensive, and you need to acquire them in advance to cast the spell, but they aren't expended like costs are. Unless noted otherwise, a locus has negligible Bulk.