This is the most fundamental of all the fundamental skills. If you can't do the single palm change then you will have the same trouble with every other method and technique. It trains the koubu and baibu steps (stepping firmly and settling firmly into the stances), snake form coiling (horizontal action), entering with the body (keeping the body upright and moving from the feet), etc.
The eight variations of the single palm change isolate particular techniques such as chuanzhang, train to the eight directions, and vary the upper, middle, and lower basin.
Action One: koubu
Action Two: baibu brace
Action Three: mabu catch the enemy's head (optional)
Action Four: koubu hide a flower under a leaf
Action Five: dragon turns its head (flat)
Action Six: place in dragon walk posture