What the type code means
Every aircraft model has a four-character ICAO type designator, published by the International Civil Aviation Organization in Doc 8643. Air traffic control flight plans and flight trackers use it. The codes are compact rather than pretty. B738 is a Boeing 737-800, A20N an Airbus A320neo, E75L an Embraer 175 with the long wing, C172 a Cessna 172, and H60 the whole Black Hawk and Seahawk family. Several marketing names can share one code. For example, every Citation Excel, XLS and XLS+ is C56X.
Not every aircraft reports its type. The type usually comes from a registration database that matches the aircraft’s ICAO hex address, so unregistered, foreign or privacy-protected aircraft can show “unknown”.