system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can you charge Nintendo Switch using a laptop but if you connect it to a MacBook you actually charge the MacBook instead of the console?
gpt
USB-C negotiates bi-directional power control and communication on a per device basis. If the MacBook USB-C controller determines that the Switch is a valid recipient for power, it will reverse the power direction and provide output power from the charging port. 

This was intentionally part of the design to lead to greater flexibility for systems.