Let’s being this conversation by answering the question what is a port. Interesting enough, there are 65,536 ports that are contained in every computer cable. So a port is basically one of the microscopic wires, fiber optics, etc. that are contained within a communication cord/wire. That is just one cord.
Now imagine a computer network and all of the cords that are used to connect it together. Each of those cords has 65,536 ports within it, as well. If information is sent out in the form of packets, and information is received in the form of packets, then it is safe to say that A packet must travel along a port, or a pathway within the entire network of cables.
If you are a car and you drive from point A to point B in a city, then you know that the shortest distance is often the fastest route, but that is not always true because of outside factors that may make you wait. The same is true of computer networks and the port/paths that information packets must travel. Believe it or not there are traffic rules that packets must obey as they travel along these little highways.
Now imagine you are a packet of information and that you have to navigate your entire computer network just to find a printer to print the information that is contained in your packet. The only problem is that you are paid according to how long it takes you to do your job. The faster you do your job the more you get paid. Suddenly, you are very concerned with finding the fastest route to the printer. This is where port forwarding comes into the tale.
Port forwarding is by definition the forwarding of a packet of information bound to one IP Address to another through a NAT. In short, port forwarding is the map that allows information to travel along the quickest route between computers. Whether or not each computer is on the same network, or if they are connected via the Internet.
If we consider the story here, port forwarding is the same as giving your car a right light and a siren so that each time it encounters a traffic intersection it is given the right-of-way and ushered along the network. This is why port forwarding is important to most of us. It allows our information to travel between points at the fastest rate possible.