I'm running XAMPP 5.6.36 on Windows, and I notice in the mysql data directory, every table has three files: FRM, MYD, and MYI. All my databases are using the default InnoDB engine. My understanding is that MYD and MYI files are only used for MyISAM, so why do these files exist? I have read several questions on Stack Overflow (like this one), where people assumed the poster was asking about MyISAM just because these files exist, and therefore gave risky advice about backing up.
Also, I just want to make sure I understand this correctly: MyISAM tables can be selectively restored from a backup simply by copying those three files. But for InnoDB, since all databases are stored in one "ibdata1" file, you can't easily restore just one db or table, you have to restore the entire data folder at once. Is that right?