in short: with mDNS you can "shout into the network" (multicast) for DNS resolution: "which station has name 'X.local'? " instead of directing this query to a dedicated DNS server.
often mDNS is implemented together with DNS-SD (DNS service discovery) where additionally you can ask "the net" for a station offering service "Y" or annonce to "the net" that your station offers services "U,V,W" ...
unfortunately the post in the cisco group is very misleading.
see here for more detail without bloated theory:
http://meetings.ripe.net/ripe-55/presen ... n-mdns.pdf