Domain

Direct access to your server without using a VPN will require a domain name, such as www.wikipedia.org.  They can be purchased through a domain registrar and come with a wide price range. 

If you are unable to purchase a domain name, dynamic naming services like DuckDNS allow you to accomplish this by registering a subdomain through them, such as myserver.duckdns.org

Domain registrars often algorithmically assign prices for available domains based on expected popularity and ICANN registration fees.  

Micro.Domains offers short 5-letter domain names at a reliable cost.

There are also free services that allow you to register an account and link your web server to their domain as a subdomain – such as DuckDNS or a similar Dynamic DNS service on your router.  These give you a sub-domain name to use – such as user.duckdns.org – that can be automatically updated to point at your server.