What is a feed dog? How does the fabric move while i am sewing?

Fabric Feed:

All sewing machines that I know of, have forward and reverse sewing to tie-in thread ends at the start and end of a seam. But what are the options when it comes to the sewing machine feed dog controlling fabric movement, moving the material forwards and backwards under the presser foot? Sewing machines are highly engineered products and can do lots of operations at the same time, as moving the fabric, in any direction?

• Feed dog: A feed dog is made of metal and has rows of pointy teeth, it moves up and through the needle plate slots to move the materials forwards or backwards, beneath the presser foot.
  
  
• Basic feed: Is where the feed dog will have only 3-points of contact with the material as it moves the fabric. The feed movement is oval-shaped, meaning the optimal feed height, to move the material, only last a short time. Depending on the fabric, it may slip undesirably against the underside of the presser foot and the feed dog.
  
  
• 6 or 7 point feed: Which are a well-thought-out and well engineered feed dog shape, it has the feed teeth, in front of the needle, as well as to the sides and rear. I meant the materials is pushes, and pulled under the presser foot for better fabric feeding and is available in mid-range models.
  
  
• Box feed: Has more to do with feed system movement than just the feed dog its self. Box feed means the feed dog lifts vertically, moves horizontally to move the material, then moves vertically down under the needle plate, and finally moves horizontally and parallel back to its starting position.
  What does this all mean? In a mid-range computerised machine, it gives a longer feed motion, less fabric slipping, and when coupled with a 7-point feed system, it keeps the materials under the foot very much under control at all sewing speeds. 
  
  
• Dual feed: Imagine, using feed dogs under the materials and well as fabric feeding teeth from the top, being part of the presser foot. There are attachments like walking even feed feet available to a similar task, but they don't compare to dual feed systems built-in to some computerised models. Pfaff have their ITD (Intregated Dual Transportation). Janome have AcuFeed, Bernette have DualFeed, Brother have Pin feed, all very clever and good for thicker or the finest fabrics as well as satins, silk, fur, leather and vinyls. Quilt and curtain makers love the dual feed systems when stitching multiple fabric layers to stop slippage.
  
  
• Sideways feed: Yes, some of the more expensive models can even sew sideways, left to right and vice versa! The feed dog with its tiny teeth can move the material to the side, as well as forward and back, allowing specialist mending stitches, 50mm wide decorative stitches, stacking and ribbon stitches.