Gyro lowpass filter
The gyro lowpass (LPF1/LPF2) attenuates high-frequency noise on the raw gyro signal before it reaches the PID controller.
More filtering = less noise but more delay (phase lag), which hurts tracking and can cause propwash. PIDoctor compares the filtered vs. unfiltered gyro FFT to show how much your lowpass removes — and whether you can raise the cutoff for less latency.