Port forwarding opens up ports on your router for other people to connect through. The ports for Unturned are 27015-27017. To open up ports/port forward, you will need to access your router. You can find your router through Command Prompt. People who have connected through your Wi-Fi connection at home can connect to your server with no need for port forwarding. However, to get a friend from another house, another state, or country to connect, you will need to port forward. Your router's manual or manufacturer's support online will have details specific to your model.