The mailcap file is used by the metamail program. Metamail reads the
mailcap file to determine how it should display non-text or multimedia
material. Basically, mailcap associates a particular type of file
with a particular program that a mail agent or other program can call
in order to handle the file. Mailcap should be installed to allow
certain programs to be able to handle non-text files.
Also included in this package is the mime.types file which contains a
list of MIME types and their filename "extension" associations, used
by several applications e.g. to determine MIME types for filenames.