步法 (bu fa) means footwork. I’ve been working on building a comprehensive list of names of steps and stances. I use the Chinese names, because translations of the everyday meanings of the Chinese words are mostly not applicable; these are terms of art. I do offer some English equivalents, especially where the English expression is well established.
弓步 gong bu (bow stance) is the long stride in which the leading foot points straight ahead and the back foot is at a 45-degree angle. How long, low, and wide the stride is varies with the individual and the style of tai chi. In the modern forms that I have studied, long and low is good, as long as you don’t have to lunge or lurch to move around, and about 8 inches in width is desirable. The weight is 60-70% on the leading foot.
In 虚步 xu bu (empty stance), the weight is entirely (or at least 90%) on one foot. The other can be in front with the ball of the foot or the heel touching and bearing a slight amount of weight. A variation is 点步, dian bu, in which the foot is pointed.
歇步 xie bu (resting stance) is a low position with the legs folded. The front foot points straight ahead and bears most of the weight. The knee of the back foot is turned in and rests on the back of the front leg. The heel of the back foot is off the ground. Xie bu can be specified as di (low), which means all the way down so the back knee is on or near the ground.
仆步 pu bu is a low stance in which the body is turned sideways and one leg is folded into a low squat while the other is extended. This stance is also called fu hu (tame the tiger), and is most famously exemplified in the taiji movement called Snake Creeps Down. Both feet face front, parallel, and the heel of the bent leg should be on the ground. The upper body should be upright.
扣步 kou bu is a pigeon-toed stance used when turning the body around.
马步 ma bu (horse stance, or horse-riding stance) is a wide stance with thighs parallel to the ground. Weight is equally distributed in plain ma bu, but the stance may be staggered left or right. It can also be easily shifted into left or right bow stance. In a general list of fighting stances, this one should probably have come first, but it is not so common or basic in taiji as in kung fu.
擦步 ca bu is the forward step in Chen style taiji, in which the heel skids forward (ca means brush or clean or polish).
叉步 cha bu is a cross-step behind. When stepping into xie bu, one foot is set down behind the other, but just behind. In cha bu, the back foot crosses well behind.
盖步 gai bu is the opposite of cha bu: it is a cross-step in front.
并步 bing bu means feet together.
丁步 ding bu means feet are together, but the weight is on one foot, while the heel of the other foot is lifted. The empty foot may point forward or to the side.
开步 kai bu is a step to the side; kai means open. In Cloud Hands, the sidestep is kai bu.
撤步 che bu is a side-facing bow stance.
in 摆步 bai bu (swing step), the leading foot is set down on the heel and then swings outward 90-degrees. The heel of the back foot releases with the shift of weight, and the hips turn.
独立 du li [bu] is standing on one leg. The standing foot is at 45 degrees with respect to the body, as is the knee, which should be lifted waist-high, with the free foot pulled in toward the center of the body for balance.
跳步 tiao bu is a jump. This generally refers to the move traditionally called Horse Jumps Over the Stream.
進步 jin bu is an advancing step.
退步 tui bu is a retreating step.
半步 ban bu is a half-step, where the back foot follows the front foot half-way, as for example, to set up Bai He Liang Chi (White Crane Spreads Wings) or Shou Hui Pipa (Playing the Guitar).
上步 shang bu means step up one step with the back leg, as in Shang Bu Qi Xing (Step Up Seven Stars).
行 步 xing bu is a walking step, usually in a circle as in Bagua Walking.
This list is not exhaustive–I keep coming across new steps! I haven’t found all the names of the shifted horse stances or the special empty step for Bai He Liang Chi (in which you set the toe in front, between the opponent’s legs, in preparation for a snap kick) or the staggered horse stance that you jump to in the fan forms (I do know there’s a special name for that, too). But this is most of them.
See also Wikipedia on Wushu Stances. Also, Jesse Tsao covers basic Taiji stances in his Tai Chi Fundamentals DVD, which is also available as Amazon Stremming Video. This book, Complete Taiji Dao, also covers many of the stances described in this post.