Please provide the detailed information for this
You can find the answer in the router documentation. You will be interested in paragraph four.
Simply put: it is tar.gz of Turris OS root. It contains base system installation.
The difference between sysupgrade image and medkit is in format and usage. Medkit is inteded to reset router to latest version but factory settings.
Okay, I got it. Thank you so much for making it clear,