There are many benefits to a 20-30 minute walk each day:
Any workout is good exercise for your lungs and heart along with the obvious benefactor, your muscles.
A simple physical act like walking gives you some necessary down time for your brain. Your brain needs time to rest and recover similar to how your muscles need a rest. So, don’t bring a cell phone with you. Just walk and let your mind wander.
If you’re walking outside, you’re also receiving an additional soothing effect to your nervous system simply from being in a natural setting.