A wide area network (WAN) is a geographically dispersed telecommunications
network. The term distinguishes a broader telecommunication structure from a
local area network .
WAN IP just like our telephone number in the real word, but WAN IP just only
exist on internet.
If you want remote access or remote control your computer, you must know your destination IP address first.
For instance, you want to call someone, you need to know their telephone number before you call them.
There are several helpful links post on the web. I found this is more
accurate one, but it is just for your reference.
You need considering to ask your ISP (Internet Service Provider) confirm your WAN IP address is correct.