The term "REPACK" generally applies to large, modern PC games that are compressed to reduce download sizes. Because Super Mario 64 is incredibly small at 8 MB, packaging it as a "REPACK" is a common strategy used by malicious actors to hide executable malware, adware, or trojans inside a fake archive or installer.
: Once compiled, these features are usually togglable in the in-game options menu.
: This is the standard file format for Nintendo 64 game ROMs in "native" (big-endian) byte order. It is the most common format used by emulators like Project64 or Mupen64Plus.