It's a 3 Pin Screw Type PCB Terminal Block - 3.5mm Pitch. The 3 Pin 5mm pitch Pluggable type PCB terminal block is a type of electronic component that provides a secure and reliable way to connect wires to printed circuit boards (PCBs). The “3 pin” refers to the number of connections available on the terminal block. This means that up to eight wires can be connected to the terminal block.