manual/include/automation.html

<p>
  <dfn>Automation</dfn> is the ability to dynamically control various aspects
  of a track's innate attributes and the attributes of any processors attached
  to it. In Ardour, automation can be used to make dynamic changes to a
  track's:
</p>

<ul>
  <li>Volume</li>
  <li>Panning</li>
  <li>Trim</li>
  <li>Muting</li>
  <li>Any attached processor's parameters</li>
</ul>

<p>
  Any combination of these can be enabled on a single track; as such, it offers
  a lot of power and flexibility over how a track will ultimately sound when
  played back.
</p>