What does spawn ,expect and send command in linux/unix
<p>The following three lines having three commands(spawn,expect,send), but what it does actually. Please explain any one<br><br></p>

<pre><code>spawn ssh -oStrictHostKeyChecking=no -oCheckHostIP=no usr@$myhost.example.com'&lt;br&gt;
expect "password"&lt;br&gt;
send "$PWD\n" &lt;br&gt;
EOD
</code></pre>