What is Dynamic DNS?

"Dynamic DNS or DDNS is a method of updating, in real time, a Domain Name System (DNS) to point to a changing IP address on the Internet. This is used to provide a persistent domain name for a resource that may change location on the network."
Wikipedia, https://en.wikipedia.org/wiki/Dynamic_DNS

Premium Members can choose up to 5 names in their Forwarded Ports: https://airvpn.org/ports page, accessible from the left tabs of their "Client Area". A name is associated to one or multiple forwarded ports, according to your preferences. You may define multiple names (one per forwarded port or ports). When a Premium member connects to an Air VPN server, the *.airdns.org DNS record is updated into the exit-IP address of that server. 

If you wish that a DDNS based name is linked to a specific device, you can link the specific device and the name to the necessary forwarded ports. By doing so, the specific name will resolve into the IP address of the VPN server which the selected device connects to. This service is useful when you need one or multiple domain names which must resolve correctly across all Air VPN servers in order to reach a software you need to run "behind Air VPN".  For example: if you want to host a game server, you can communicate to the players the DNS name and the destination port, and then freely switch Air VPN servers.

Notes: TTL (Time-To-Live) is one hour. If you change VPN server, on average 30 minutes may be needed before other users can resolve correctly your domain name. A longer time might be necessary: some public DNS (for example Google DNS) sometimes ignore TTL in their caching system. DNS are created or updated when a connection to an Air server is performed. They are deleted only if you disable the system (i.e. you delete the name from the forwarded ports panel). The latest IP address is NOT removed during disconnection or connection retry.