Footwork is the best form of defense. The reason is that if you're not there to be hit, how can they hit you?
Other defenses include slipping, rolling, leaning back, blocking, and parrying. They can all be great, but with these, your feet are still in range so there's a chance you can still get caught! Also, if you do get hit while you're moving away from a shot then you will take the sting out of it.
Footwork gets you in range to get your shots off and allows you to move out of range and away from danger, setting you up for power punches. Good footwork equals good balance, which means you can have better speed and accuracy. This allows you to punch harder.
If you look at every great fighter past and present, they have all had impressive footwork - even if you look at the likes of Mike Tyson. To the uneducated eye he can look like he is flat-footed and be plodding forward, but he had some of the fastest feet ever in the heavyweight division. The way he could cut his openers down and pivot to get that famous punch power in his shots is some of the best footwork you will ever see!
You don't really think of footwork in the heavyweight division but all the great champions have all had great footwork, the likes of Ali, Lennox Lewis, Klitschko and now Anthony Joshua's footwork is fantastic!
This video I made below shows some of the common mistakes we see with footwork and how to fix them.
From a fitness point of view, moving your feet after you throw your punches really helps increase the calorie burn and give whoever you are teaching a much better work out. We teach you all this and more at the Box ’N Burn academy where we certify trainers on how to teach boxing.