There often is a bit of confusion between using a "Unique IP" and a "Sub-domain/domain" to connect to servers. These two are not the same thing and are actually quite different. We'll give a brief and detailed explanation of both so you can understand what the differences are and get setup with what you want.
Unique IP:
This means your IP address is on its own IP unique to your server and not shared with other users. This allows your server to run on the default "25565" port. The advantage of this is that you do not require to enter a port to join.
Sub-domain / Domain:
This is similar to the URL you enter into your browser to connect to web-pages. But it also has other features and "DNS" properties which will allow you to connect it to your server IP and join your game through it. A lot of people confuse this with a "Dedicated IP" and they are NOT the same. Basically as sub-domain for instance, looks like "mc.example.com" and a domain looks like "example.com".
If you want a domain, then that comes at a price. However, its fairly cheap and most popular domain providers offer them at $9-10 per year.
