For a good explanation of what the meta description is and what it does, along with lots of other uselful starter information, see
http://www.google.com/webmasters/doc...rter-guide.pdf.
You're half right. Linking to them is just an outbound link, which won't improve your ranking much. Linking to them and
having them link back to you is the reciprocal part and is better. And they should be relevant as well, don't just submit to every link farm or directory you can find.