https://www.youtube.com/watch?v=qum_S8GvDRw&list=PLSzYQGCXRW1Gk3C7fh7tVE92UKOn-chtg&index=4

https://discuss.ardupilot.org/t/mavlink-step-by-step/9629

MAVLink is a message protocol, designed to exchange information between a drone and a GCS or a subsystem (ex: gimbal controller), using a serial communication channel.

It is binary information, so without interpretation, it is not readable by humans.

A MAVLink frame can be 8 to 263 bytes long:

MAVLink Message - sent from drone to GCS

MAVLink Command - sent from GCS to drone