It’s a mosfet. They technically have four terminals (as a result of manufacture).

To be clear, there is no io here. It’s not an IC. What’s inside is only technically a chip, as it’s a single big transistor (typically used in power control circuitry).

There is the usual three: source, gate and drain, which are next to each other on the bottom (The mosfet has had its pins bent 90 degrees). The gate accepts a voltage, which then controls how much power can flow across the source to the drain. This can be used to have something like an arduino, operating at 5V, control a 100V circuit. A tiny signal controlling a far larger current.

The fourth is the body terminal, taking up the entire back, it usually goes unused (in large discrete transistors like the one pictured) and is internally shorted to the source. You do often see the large metal surface of the body terminal used for cooling, by having it contact a heatsink or the pcb, as mosfets used for power supply or motor control can get quite hot.

Hence why the girl is using it as a cooktop :D