Lets say you have a computer at your house that you want to connect to the internet and serve up some files for people to see.
Your internet service provider (ISP) charges you a large amount of money for internet service on a monthly basis and they still give you a dynamic IP address. I guess I could starve my family and pay for a static IP address, no, I'm too smart to throw them more money.
I could just find a dynamic DNS service that would give me some randomSubdomain.some_already_defined_catchy_domain_name.com. Then I just have to remember that and give that out to who ever I want to share these files with.
Instead, I could use the domains that I want and point my DNS entries to my dynamic IP address. Oh crap, what if my ISP decides to give me a new IP address? Argh, then I have to log into my Domain Registrar and update my DNS entries to the new IP address.
Thanks to free DNS services such as zoneedit.com or dnsever.com or plenty of others you can use their servers to maintain your DNS entries for "free". I know that zoneedit and dnsever both offer "free" DNS service for 1 or 2 domains.
So now comes the question about when my home's dynamic IP address changes.
These DNS services provide you a way in which you can update your DNS entries via simple scripts/web addresses that will update your entries for you.----ZoneEdit----
wget -O - --http-user=<YourZoneEditUserName> --http-passwd=<YourZoneEditPassword> 'https://dynamic.zoneedit.com/auth/dynamic.html?host=<YourZoneEditHostName.com>&zones=<YourZoneEditZonesName.com>'
wget -O - --http-user=<YourDNSEverUserName> --http-passwd=<YourDNSEverPassword> 'http://dyna.dnsever.com/update.php?host[<YourDNSEverHostName.com>]&host[<AnyOtherOfYourDNSEverHostNames.com>]'
These two are for use in a system with wget installed, either Linux or Windows with Cygwin installed. Then you just have to figure out when your dynamic IP address from your ISP changes and then issue these commands and they will updated the DNS entries to point to the new IP address that your service provider just gave you.
Now when you want to get back to your house you just use your own domain.
The other thing you can add to this is that when you verify that your IP address has changed that your system will email you the new IP address so that you can know before as soon as your ISP changes things up.
If you have any questions/comments please let me know. This is post is more for a friend who is tired of paying for hosting!