When you walk, significantly less weight is bearing down on the ground (or treadmill) with each step than when you run. Because of this, a good walking shoe requires less cushioning than a running shoe. While you wouldn't want to walk in a shoe without any cushioning, of course, the additional padding you'll likely notice in the heel and forefoot of most running shoes may add more weight than you need. A lighter shoe that still provides some cushioning is preferable for regular use and longer walks, as this will keep your feet comfortable without adding extra weight.
The point of impact changes when you walk versus when you run. While runners strike the ground anywhere from the forward part of the heel through the midfoot to the foot's ball, a proper walking stride will cause the heel to strike first. Because of this, the type of shoe and the ideal heel height vary by activity. Runners need differing degrees of built-up heels depending on their specific strike pattern, while walkers should look for shoes with the least height differential between the heel and the toe. Be sure to pay attention to the actual heel rather than the shoe's outer sole, as some styles may appear to have a higher heel that, in fact, sits lower inside the shoe.
If you suffer from any foot conditions, especially plantar fasciitis, choosing the right heel height can be tricky. It's important to consult your podiatrist before starting a new fitness routine to discuss the right footwear for your specific condition and desired activity, as there are some additional features you'll want to keep in mind.
A flared heel can be great for runners, particularly trail runners, as it provides a bit of extra stability. Because the heel should be the first point of impact when walking, however, you'll want to look for an undercut or straight heel instead, which aids with the natural forward rolling movement that occurs when taking a step.
Both running and walking shoes should be moderately flexible; where that flexibility is centralized, however, is what sets them apart.
While most running shoes flex at the arch or midfoot (again, this relates to how the foot meets the ground when running), walking involves a forward rolling motion starting with the heel and ending with the toes pushing off the ground. This is best suited to a shoe that flexes at the forefoot.
In addition to the above, it's important to pay attention to any foot-related problems that may require special features or additional support. For example, if you have diabetes, finding a walking shoe that is also SADMERC and PDAC approved is a great way to ensure a proper fit.
With a better understanding of the difference between walking shoes and running shoes, you'll now be able to find the perfect footwear for your specific needs.