A walking foot on a sewing machine is its main component with which the mechanism of feeding the work piece through the sewing machine is done when it is being stitched.
Normally when you use a sewing machine, its feed dogs make contact only with the bottom layer of the fabric because of which stitches are unevenly fed to the fabric. But with the help of a walking foot, the stitches are evenly distributed to the top and bottom layers of fabric.
As you know, the purpose of the walking foot is usually used on fabrics that do not easily stitch evenly. The most common fabrics on which it is used are sticky fabrics, bulky fabrics, thin fabrics with multiple layers, and stretchy fabrics.
One of the most important purposes for using the walking foot is to match the seam lines. Whenever you sew cuffs or waist seams then it becomes very important to create matching seam lines on them. And that is the time when walking comes in handy.
If you want the stitches to be equally distributed on a pattern then using a walking foot would be a great choice. It makes sure that the pieces of the prints are aligned together as they were before being cut.
You should have noticed that whenever you topstitch a fabric, it still consists of some drag lines at your hem or button placket. A walking makes sure that nothing of this happens by keeping all the layers even, to provide you with nice and flat edges.
The nature of the stretchy fabric changes its shape whenever it is stretched. So, when sewing the stretchy fabric the stitches are not distributed evenly, but it can be done easily with the help of a walking foot because it does allow the fabric to get out of its shape.
If you sew then you must know about the difficulty when sewing the slippery fabric, and the need for excessive pinning for stabling the fabric. With the help of walking, you do not need to do any of that, it helps you to easily sew the slippery fabric.
It will be very bad to use a walking foot if you are sewing reversely as it is not designed for that. It is also difficult to do decorative stitches with a walking foot because it does not allow side-to-side fabric motion.
The walking foot is an essential tool for sewing as it provides you more stability and visibility, especially when you are machine binding or quilting. An open-toe walking foot would be good as it allows you to see where the needle hits exactly.