🎥 Betaflight
The most widely used open-source flight-controller firmware for FPV racing and freestyle drones.
What it actually does
Betaflight is the open-source flight-control firmware that runs on most FPV quads. It is what interprets your stick inputs and the gyro readings and decides what each motor should do, thousands of times a second. Learning to configure it is most of learning to build quads.
In practice
The configurator lets you set PID tuning, rates, filtering, failsafe, receiver protocol, motor direction and flight modes. Sensible defaults have improved enormously, so most people now fly a new build on stock tuning and adjust from there rather than starting from scratch.
Worth knowing
Always remove propellers before connecting to the configurator and testing motors. This is the single most important habit in quad building, and the reason experienced builders say it every time.