If you don't setup a static IP address the port forward will probably work the first time.
But after restarting your computer it may use a different IP address.
When IP addresses are assigned dynamically, it is the router's job to assign them.
Every time a computer reboots it asks the router for an IP address.
If you want to know more about how networks work check out the information here.
Your router most likely assigns dynamic IP addresses by default.The router then hands the computer an IP address that has not already been handed out to another computer.This is a very important because when you set your computer to a static IP address, the router doesn't know that a computer is already using that IP address.If they ask you why you need them, simply tell them you are trying to setup a static IP address on your computer.If they try to sell you a static external IP address, don't buy it.When the start menu appears simply type cmd on your keyboard and press enter.Step 2: A window similar to the one you see above should appear on your screen.Step 1: Open up the Windows 10 start menu by pressing the Windows key on your keyboard.You can also open this menu by clicking the windows icon in the lower left corner of your screen.It's okay if it doesn't look exactly like the one you see above.In this window you need to type ipconfig /all and press enter.