It can be an orb, rod, staff or wand.
This item is needed to cast spells. There are two types of focuses:
– One that must always be in your hand when you cast a spell that requires a material component (i.e., a quartz crystal), such as the focus of transmutation magic–the alchemist’s stone–which is usually held in one’s palm; and
– Another that can rest on the ground near the caster during casting of spell with no problem, as for example for druidic astral projection spells while resting in circle dance at full trance level before awakening and leaving previous location which they transited into new locus by spiriting body and soul into otherworlds.
The latter can be even an item embedded in clothing or armor, whereupon it becomes unnoticeable. For example, the brilliant energy of sun soul calls for focus that is not necessarily wielded at hand but built into the caster’s helm to avoid its disadvantage which is -2 on every Constitution save roll while concentrated during trance level casting. Of course, there are also exceptions to this rule. For example, fireball can be cast with nothing but verbal component in hand while the orb of illumination is simply held in the other.