In this context an air gate is a type of sensor which gives a pilot an indicator when their drone has passed it. In drone racing this can be used as checkpoints, at finishing lines and to chart ...

His Arduino code reads the NAND using the notoriously slow digital_read() and digital_write() commands and then dumps it over the serial port at 115,200 baud.

Official Arduino Example Tutorials: The Arduino computer software is loaded with tons of examples for you to use in your own code or to run through as a learning experience.