This may be a dumb questions but what does this stand for and why is it important?

Thanks,
Tim

I am no expert but it is Forward of Center. It refers to the center of gravity of the arrow and where it lies relative to the centerpoint of the arrow. It is expressed as a percentage.

No, it is not a dumb question, you gotta find out somehow.

To visualize.  Draw a line around your arrow at the measured center or midpoint.  Lay it across your extended finger, on that line.  Does it balance ?  Move it until it does.  Probably the balance point is closer to the tip than to the rear.  The closer to the tip, the more % FOC your arrow is weighted.  There are earlier posts discussing the virtues of this phenomenon.

There is discussion that, up to a point, more FOC weighting allows the arrow to fly better and to penetrate better.  Remember...up to a point.  It also can change the effective spine of the arrow, again, to a point.  (OK no pun intended on the point business).
Later ChuckC

Great explanation, I just purchaed more carbon arrow, but I added the 50 grain brass inserts and my point weight is close to 160gr. my old FOC was 13% my new FOC is now 16.2% and arrow flight is noticeably better. It was good before, but now, WOW. to go up the 3% it was an increase in weight of 15 rains and that moved the FOC point 1" forward.

Richard...on the other end, back years ago, during my dark times, I used Beeman carbon shafts, not much fletch and tried 125 grain broadheads.  The arrow flew down range with the rear end spinning, I mean, not rotating, but spinning in a circle of maybe 4".  Went to 100 grain heads and they flew great.  I imagine using 5.5 inch feathers (heck...4" maybe ...I was using not too much at the time) would have also helped straighten the flight as well.

Tim, one of the fun parts of doing it yourself is that you get to experiment with your gear and you learn so much more about what makes it work and what makes it better for you.
ChuckC

Chuck, I have been using 4" for awhile and that what these are. Just wondering what would happen if I add 20 or 30 more grains up front, but I am real happy now.

Try it and see !  Won't really know till you do. I currently shoot woodies with 5.5 inch feathers.  They can straighten out an arrow 50 pounds (kidding) out of spine.  But oh, watch those cross winds.  

Actually, I really really enjoy watching them fly.  I remember a few years ago, a friend and I were shooting at a range, and we stepped back.....way back, and shot some arrows at maybe 90 yards or so.  For some that is no problem....for us...well.....    I watched that arrow and said out loud.. "wow that was beautiful !".  He asked if he hit the target and I said "I haven't a clue, but was it ever beautiful !"  We both laughed ourselves silly.

I guess I am in this game for other reasons than many.
ChuckC

Thanks Chuck, your set up sounds similar to the one that I am going to attempt to build.  It will be 3 5.5" fletch.  Just heard a lot of the guys that build arrows talking about "FOC" and was not sure what they were talking about.  

Thanks again,
Tim