1. System Firmware (aka: OpenTX): Computer code that tells the RF firmware what to do. This includes any adjustments you might make on your transmitter, the number of channels used and their order, any switch assignments, special rates, etc.. This is what you change when you update OpenTX to add new features, fix software glitches, etc.
2. Transmitter RF Firmware: Computer code that generates the radio signal. In the Taranis, this is known as the XJT firmware because the internal RF module of the Taranis uses it. The XJT firmware is not the same as the OpenTX firmware. FrSky provides a Windows Only program to perform the XJT update.