Tools are items that the player uses to produce an effect in the world, rather than creating a Block or planting a plant. Some are used to dismantle World tiles, such as Blocks, Walls, or freeing placed items, to convert them into carryable objects. Pickaxes, axes, and hammers can also be used as melee weapons, of which some are actually made to be weapons. (Taken directly from terraria wiki)
N Terraria offers 6 tools, which we will be listing below.