Also called a Cat Stance, this stance is generally used as a prelude to an attack or an intermediate step when retreating. Sometimes it might be considered a mixture of both.
In this stance one leg is placed forward of the other, the front knee is bent, and the ball of the front foot is placed on the floor. The front leg is significantly bent and only a small percentage (from 0% to 10%) of your weight is placed on the front leg. Nearly all of your weight is on the back leg, which is slightly bent to enhance your balance and to allow faster movement out of this stance. You should be generally erect and let your weight sink down into and through your hips to your supporting back leg.
Some martial arts styles suggest that the front foot should not support any weight. We think this depends on your application. You may well encounter situations where being somewhat rooted upon your front leg is advantageous. Of course, putting too much weight on the front leg makes you less mobile and agile. So we suggest the front leg should bear little to no weight when adopting this stance. It is harder to adopt the stance with no weight, so this should be what you strive for initially. But in practice, you will find that you often have some slight weight on the front leg.
The back toes (and back knee, to a lesser degree) point off at about 30° and the front toes and knee point forward (to local octagon angle 1).
This stance is almost always a rapid transition stance. It might be used to prepare to deliver a Mae Ashi Geri, pull your opponent off his or her structure, or retract from an opponent momentarily so that you can step around his or her front foot. Whatever the reason, the stance is almost always used to initiate a subsequent movement. For this reason, the stance is seldom done in a low or deep position.