The CC pin, short for Configuration Channel, is one of the pins inside a USB-C connector. It is used to detect which way round a cable has been plugged in, since USB-C is reversible, and to identify the roles of the two connected devices, such as which one is the power source.
Beyond orientation, the CC pin is central to how USB-C negotiates Power Delivery, since the initial communication about how much power to offer and request happens over this channel. It is also how a device detects whether a cable carries an e-marker chip reporting the cable's capabilities.
Most users never need to think about the CC pin directly, but it is the quiet mechanism behind features that feel automatic, such as a laptop and charger agreeing on the right voltage the moment they are connected. See our USB-C guide for the bigger picture.