Firey...A fuge is a place to grow pods, keep little critters that are benficial to the tank, or to put flora such as cheato in so it doesnt get eaten all up by herbivores.
There are a few types...hang on inside, hang on outside, ones that use pumps to get water in and out etc that are basically fish tanks themselves...
I just started using one myself a few weeks ago. I have a hang in the tank, where the output from my filter blows through it...damn i gotta get some pics...i promise tonight.
I have cheato in there. I was told cheato will help with trates and phosphates. So far, I have noticed a slight reduction in both.
Others on the boards have awesome fuges and can tell you a bit more...
PS- I'll tell you, things changed from years ago when I had my tank back then. But if you learn to test things, know what the results mean, and can adjust the parameters, the tank wil look awesome. I'm impressed what difference from years ago on the health of things, and although I never had coral back then, it was easy to do once tank was stable.
Have fun! Post any q's anytime, thgat's what i did and i learned a real lot.