Almost all Entry Level Internet accounts are Dynamic. Meaning your External IP (aka WAN IP) is assigned by the ISP?s will. External Static IP usually cost more and comes with a Business account.
If you are connecting One computer directly to the Internet modem the computer would be assign with the External IP.
But you use a Router. In such a case the External IP stays the same (I.e. depends on your ISP on Not on you or your Router).
The computer or computes IPs is not anymore the External IP, it becomes a private IP that can assign as Static by you, or as a dynamic that can be assigned by the Router? DHCP server.
What ever you use for the Private IP is not reflected to the Internet. The roll of the Router is to Mitigate between your LAN (Private IPs) and the Internet (External IP).
If you want to be able to connect to your computer from the Internet and you have an External Dynamic IP look at option 3 here,
http://www.ezlan.net/myip.html
As an example my computer private IP with a Router is 192.168.1.100
My External IP today is, 68.173.33.202 as assigned to me by Time Warner Internet Cable Service.
How do I find the IPs? see here,
http://www.ezlan.net/ip_mac.html
All of the above is the same for Wired computer as well as Wireless.
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