debian_debian-policy/debconf_spec/include/priorities.xml

<table frame="all">
  <title>Supported priorities</title>
  <tgroup cols="2">
    <thead>
      <row>
        <entry>Priority</entry>
        <entry>Description</entry>
      </row>
    </thead>
    <tbody>
      <row>
	<entry>low</entry>
	<entry>
	  Very trivial items that have defaults that
	  will work in the vast majority of cases.
	</entry>
      </row>
      <row>
        <entry>medium</entry>
	<entry>
          Normal items that have reasonable defaults.
	</entry>
      </row>
      <row>
	<entry>high</entry>
	<entry>
          Items that don't have a reasonable 
	  default.
	</entry>
      </row>
      <row>
        <entry>critical</entry>
	<entry>
	  Items that will probably break
	  the system without user intervention.
        </entry>
      </row>
    </tbody>
  </tgroup>
</table>