1/4in Jack

Stereo TRS

These are like the standard Mono Jacks that are used in most guitars, with the exception that there are 3 connectors instead of 2 (Tip/Ring/Sleeve aka "TRS"). These are required for many guitar electronics upgrades, such as adding Active Pickups or other Active Electronics that run off a battery. It can also be used to double your guitar's signal (with the proper cables and splitters, you can run your guitar to 2 Amps at once).