Avionics software is the computer programs that help airplanes and other aircraft work properly.
You see, airplanes are very big and complicated machines with lots of parts that all need to work together. For example, there are engines that make the airplane move, wings that help it fly, and a cockpit where the pilots sit and operate the controls to fly the plane.
But there are also lots of electronic systems that help the airplane work correctly. These systems are called avionics, and they include things like navigation, communication, and safety systems.
Avionics software is the special computer programs that help these systems work correctly. For example, avionics software might include a program that helps the pilots navigate the airplane by showing them where they are on a map, or a program that automatically adjusts the plane's altitude and speed to avoid bad weather.
The people who create avionics software need to be really careful and make sure it works perfectly, because if there is a mistake, it could cause a big problem for the airplane and the people on board. That's why they test and double-check everything so many times before the software is ever used in a real airplane.