An Arcane Focus is a specific item that an individual wizard can acquire in order to magically boost their spells and manipulate their magic. Without this focus, the spell will not work as desired or at all. It may be made of metal, stone, ceramic or glass and come from any material that makes sense for the player’s world/home plane. To cast a spell it must be carried in one hand while casting.
A device used by wizards during spellcasting to imbue magic into their incantations when they cannot use verbal components or speak at all (& other situations). Arcane focus is typically created two ways: one way being an object with a natural magical ability and metal objects that are etched with runes and symbols.