The walking foot or even feed foot attachment for your sewing machine can look a little menacing if you are new to sewing but they are really a gentle giant.
These images show my worn & battered foot that I could not do without (it's my third!). The function of the walking foot is to feed your bottom fabric through with the top fabric evenly. Prevents some fabrics from slipping as it has it's own set of feed dogs that move in a walking motion over the fabric.
It works best when sewing multiple layers together and is a favourite among quilters. Sewing with PVC is almost impossible to sew without one, appliques and thicker fabrics also benefit from this type of foot. They also come with a quilting guide which is a metal bar attachment that sticks out to the side ~ I have never used it though.
Some of the newer machines come with a walking foot attachment built into the machine. It usually sits to the back of machine near the presser foot lever and can be engaged when needed.
You will need to purchase an attachment that is specific to your machine. This one is for a Janome and costs approx $65.00 - $70 . It is easily connected by removing your normal sewing foot and putting the walking foot on in it's place. The arm sits over the needle clamp screw.