Welcome Guss!

A helic or off set refers to the degree of twist to your fletchings. A straight fletching is just that, straight, An offset (which is what I shoot 4 degree offset) has a slight twist to the fletchings which will cause your arrow to spin as they travel foward. A helic is a great degree of twist. To visualize check out this link:

http://www.above-timberline.com/Gold%20Tip%20Arrows.htm

Scroll down a couple of inches until you can see the three arrows. The pictures show what they look like and the boxes below describe the benefits and drawbacks to each type of fletching.