The torch is an item in The Witcher 3: Wild Hunt. It may be equipped in one of the pocket slots in the inventory panel for use as a light source.
In the inventory, torches are listed under the Weapons tab though they cannot be used to deal damage in combat. A torch may be equipped during combat, though it would prevent the player from performing strong attacks, as those require both hands to carry out.
Stepping into flammable material such as swamp gas with a torch equipped will cause that material to ignite, which would deal damage to the player and possibly knock them back.