suffixes(7) -- Linux man page
suffixes - list of file suffixes
It is customary to indicate the contents of a file with the file suffix,
which consists of a period, followed by one or more letters. Many
standard utilities, such as compilers, use this to recognize the type of
file they are dealing with. The
utility is driven by rules based on file suffix.
Following is a list of suffixes which are likely to be found on a