An Amiibo BIN file is a digital "dump" or backup of the data stored on an Amiibo figure's internal NFC chip. These files are typically and contain a unique ID that the Nintendo Switch or 3DS uses to identify the character.
: If your physical figure is lost or damaged, a BIN file ensures you don't lose the character's progress or levels. amiibo bin files link
The Ultimate Guide to Amiibo BIN Files: Backups, Emulation, and What You Need to Know An Amiibo BIN file is a digital "dump"