Port forwarding is where you connect to a port on a gateway machine and it automatically forwards you to another port on another machine. It can be useful in a very wide range of situations, including bypassing firewalls or redirecting traffic from a public network to a private network (or vice-versa). Combined with lines in your windows\system32\drivers\etc\hosts file you can even redirect where outgoing connections go.
Apart from its obvious graphicalness, this version allows you to set up any number of port redirections. You can see how many connections are being redirected and you can disconnect them if you feel the need. You can save the redirections you have setup and load them again later.
usage: trivial_portforward [port to listen on] [ip of host to connect to] [port to connect to].