Family Shield is a free filtering service provided by OpenDNS. I use OpenDNS and like the concept so I encourage others to take a look at Family Shield (or also use OpenDNS). Actually, I would be hard pressed to explain the difference between FamilyShield and OpenDNS. It looks to me like FamilyShield is an install service and OpenDNS allows more user options once installed. Perhaps I am wrong.
Here is how OpenDNS works (I do think I understand this). Web locations are identified by ip numbers and people are used to functioning based on web addresses (ndwild.psych.und.nodak.edu vs. 134.129.172.86). A computer called a DNS server takes care of the conversion. This computer could perform additional functions (e.g., filtering). So, the company OpenDNS offers the use of their DNS servers to offer these additional functions. I guess the company hopes that larger organizations will purchase additional services.