It’s essentially a mix of studying medicine and informatics. We learn partially about health, the human body, and exactly what doctors and the like do, while also being taught how to reliably process and transmit information - such as through HTML.
Hence, we can act as the postal pigeons between general practitioners and hospitals, inter-hospital, and intra-hospital, since miscommunication is a critical error when a single wrong dose can doom a patient, and GPs don’t really have one shared approach when it comes to writing things down - heck, some of them still fax things!