Generally taught as the first set, it is full of extremely useful fighting combination's, teaching the student how to move, strike and kick. Not very flashy, but designed to impart basic competence and aggression (forward movement) from the beginning.
I was told it translated as "through the joint" fist, referring to the method of punching used.
From personal experience, I have seen students who had not trained formally for about 15 years, able to perform the set - it is drilled that intensely and is that effective.
By the way, the name of the style, Yau Kung Mun, translates as "Sect of Flexible Power". A word by word translation is "Soft Hard Door".