What is Dynamic DNS?

First a step back.

Communication on the internet happens because every end-point has an IP address. IP addresses are like phone numbers on the internet. But IP addresses such as 192.168.245.123 are a little hard to remember for every website you visit so we have domains and hostnames. In order for an IP address to be associated with a hostname a computer will ask a DNS server (or Domain Name System server) which resides somewhere on the internet what IP address is associated with a certain hostname. When one DNS server doesn't know how to answer a specific request, the DNS server is setup to ask other DNS servers for help.

Now we have 1 problem. Say you want an easy way to access your home network. Different routers will allow you to access different items within your home. But because your IP is constantly changing due to how your ISP's network works, you can't easily setup a traditional DNS record to associate the IP address your ISP gives you.

Enter the invention of Dynamic DNS. Services such as no-ip.com provide your router a way to edit DNS records on their DNS server when the ISP assigned IP address changes. You put in your account information, the DNS record you want to keep up to date and the router does the rest.

So if you need remote access back to your network check out the following websites. Both provide free dynamic hostname options and are supported by most home router manufacturers:
http://www.no-ip.com
http://www.dyndns.com