system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: if I connect two electronic devices via USB-C how is the source and the sink determined for charging?
gpt
Every usb-c device has a usb controller chip inside.  The controllers determine among themselves which is the "charger" and which is the "device needing to be charged".

Usually the laptop or pc identifu as the "charger" and your phone or iPad are "devices".