MY = Model Year, sort of a "version" number.
Quick words...
Auto OEMs work on an annual cycle plan, but the release dates for improved models don't align with calendar year changes, for example 19MY in UK was available from middle of 2018. There will also be different contents in a given MY in different geographies, driven by legal and market conditions.
(I used to work on automotive configuration systems :ugeek: )
(full answer would be TL;DR :lol: )