Fontconfig does the following:

    * discover new fonts when installed automatically, removing a common source
      of configuration problems.
    * perform font name substitution, so that appropriate alternative fonts can
      be selected if fonts are missing.
    * identify the set of fonts required to completely cover a set of languages.
    * have GUI configuration tools built as it uses an XML-based configuration
      file (though with autodiscovery, we believe this need is minimized).
    * efficiently and quickly find the fonts you need among the set of fonts
      you have installed, even if you have installed thousands of fonts, while
      minimzing memory usage.
    * be used in concert with the X Render Extension and FreeType to implement
      high quality, anti-aliased and subpixel rendered text on a display.

WWW: https://www.freedesktop.org/wiki/Software/fontconfig/