Wire

Wires are used to connect various mechanisms with their triggers (Pressure Plate, Timer, Switch or Lever). Wires embed into Blocks and can only be seen while you are holding an item that is related to the wiring mechanics, such as pressure plate, wrench, or switch. Wires can be laid anywhere with a Wrench and gathered with a Wire Cutter.

Items that can be triggered by using wires include almost any Light source (notable exceptions being the Water Candle, Skull Lantern and plants), Doors, Dart Traps, Active/Inactive Stone Blocks, Pumps, Explosives, Music Boxes, and certain Statues.

Wires, Pressure Plates, Switches, Levers, Wrenches and Wire Cutters are sold by the Mechanic.

Connections made with wires may not contain more than 1000 wires, otherwise they will not work.

You can get free wires in the underground. Just buy a Wire Cutter from the mechanic. Then anytime you encounter a trap, you can harvest the wires, as well as other components.

You can store wires in your ammo slots.

Trivia
This is probably inspired by Redstonean item from Minecraft, a game that the Terraria developers have said they take inspiration from