One example of why port forwarding is great is security. Downloading email and browsing the Internet in such a way that the immediate (local) network does not know what you are doing. All it sees is encrypted SSH traffic, like that used when you type on RedBrick normally.
The example being given is to use your Redbrick account to port forward data via Redbrick. You can then configure local applications to use the tunnel rather than the usual route over say insecure wireless or hotel wifi thereby hopefully securing your data in transit.
There are some good online guides and if you read this you should be able to deduce the basics of how SSH works with port forwarding.
There are two ways of getting SSH to work on Windows.
PuTTY has built-in support for port forwarding.
OpenSSH for Windows
You can download and install OpenSSH for Windows and then use the same command as you would for unix, if you don't want to use PuTTY.
If you read the neworder guide above you should have a good idea of how to build the SSH command for the forwarding, like so:
ssh -D 1337 firstname.lastname@example.org
If you want to connect to RedBrick IRC with your own client you will need to use port forwarding to do this.
The process is the same as the above, just using different addresses and port configurations.
remote address: irc.redbrick.dcu.ie
remote port: 6667
So for this it is instead using a local forward. So unlike the dynamic forward, instead set the option to be local, and add the destination as being irc.redbrick.dcu.ie:6667
On CLI this is:
ssh -L 6667:irc.redbrick.dcu.ie:6667 email@example.com
Now, just tell your IRC client that your IRC server is localhost :)