Add Emoji to Linux Fontconfig (edited to fix broken fonts for Zoom video conference)

57-add-emoji-support.conf

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<!--
Author: Santiago Saavedra <ssaavedra@gpul.org>, Kyle Lacy
License: CC0
Year: 2016-2017

Install:
  Copy to $XDG_CONFIG_DIR/fontconfig/conf.d/57-add-emoji-support.conf
  Run fc-cache -f

Description:
  This fontconfig script is an update to Santiago Saavedra's original emoji
  fontconfig script. It uses Noto Color Emoji instead of EmojiOne color,
  and it also tweaks the match rules to fix some broken apps (namely, Zoom
  video conference, which has a weird font rendering issue if the original
  script is used).

-->
<fontconfig>
  <match>
    <test qual="any" name="family">
        <string>serif</string>
    </test>
    <edit name="family" mode="prepend_first">
      <string>emoji</string>
    </edit>
  </match>

  <match target="pattern">
    <test qual="any" name="family">
      <string>sans-serif</string>
    </test>
    <edit name="family" mode="append" binding="same">
      <string>emoji</string>
    </edit>
  </match>

  <!-- Hack to fix font issue in Zoom when the above match is applied: -->
  <match target="pattern">
    <test qual="any" name="family">
      <string>sans-serif</string>
    </test>
    <edit name="family" mode="append" binding="same">
      <string>DejaVu Sans</string>
    </edit>
  </match>
  <match target="font">
    <test name="family" compare="eq">
      <string>DejaVu Sans</string>
    </test>
    <edit name="family" mode="prepend_first">
      <string>emoji</string>
    </edit>
  </match>

  <alias binding="strong">
    <family>emoji</family>
    <default><family>Noto Color Emoji</family></default>
  </alias>

  <!-- Alias requests for the other emoji fonts -->
  <alias binding="strong">
    <family>Apple Color Emoji</family>
    <prefer><family>emoji</family></prefer>
    <default><family>sans-serif</family></default>
  </alias>
  <alias binding="strong">
    <family>Segoe UI Emoji</family>
    <prefer><family>emoji</family></prefer>
    <default><family>sans-serif</family></default>
  </alias>
  <alias binding="strong">
    <family>EmojiOne Color</family>
    <prefer><family>emoji</family></prefer>
    <default><family>sans-serif</family></default>
  </alias>
</fontconfig>

hello, thank you very much for the code, that's really great! but how exactly does it work? I haven't been working with Linux for long.
Thank you

COCCOME85
Copy to $XDG_CONFIG_DIR/fontconfig/conf.d/57-add-emoji-support.conf
Run fc-cache -f