DNS, or Domain Name System, controls your domain name’s website and email settings. When someone visits your domain name, the DNS settings control which company’s servers are used.
DDNS stands for Dynamic DNS, or more specifically, Dynamic Domain Name System. It’s a service that maps internet domain names to IP addresses. However, unlike DNS that only works with static IP addresses, DDNS is designed to support dynamic or changing IP addresses.
This DNS and Dynamic DNS settings guide [PDF: 182KB] will show you where to find and change these settings within your router settings page