Commodore 64 binary executable
A Commodore 64 binary executable is intended to be run on a Commodore 64 or on another machine that is emulating one. These files are often stored with the extension .prg when kept in filesystems that distinguish types by extension. (In the original Commodore environment, they generally didn't have an extension but had file type "PRG" in the directory structure.) Files of this type might be binary executables, tokenized BASIC, or other sorts of data files; even text files are sometimes stored in PRG format instead of TXT, so the file type doesn't give much information about what sort of data it is.
The first two bytes in a PRG file are the memory address that the file should be loaded into (in little-endian format). For a C64 Commodore BASIC tokenized file, intended to be loaded into $801, these bytes are $01,$08. Note that these bytes will be ignored (i.e. a PRG file will be loaded into $801) UNLESS the LOAD command had a non-zero parameter after the device number. i.e. LOAD "*",8 will load a file from device 8 (the typical device number for a disk drive) into $801, while LOAD "*",8,1 will load a file into whatever memory address is specified by the first 2 bytes of the PRG.