suffixes(7) -- Linux man page
NAMEsuffixes - list of file suffixes
DESCRIPTIONIt 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 make(1) utility is driven by rules based on file suffix.
Following is a list of suffixes which are likely to be found on a Linux system.