In Shaolin Kung Fu, that is actually a combination of a few different moves. Forms will typically encode movements in combinations like this, for multiple reasons. One, it makes it easier to remember large amounts of moves, as forms were typically used to preserve techniques where handwritten manuals weren't sufficient. Also, when fighting in real life, you never will be using a single technique in isolation and will often have to combine techniques fluidly. This translates into the fluid movements and transitions in forms, and the seemingly superfluous arm and legs movements.
I'll break down the different parts of the stance, according to my own training in Northern Shaolin Kung Fu Wu Su. Different styles may have some differences in detail, but probably will have similar constructions.
The diagram is demonstrating someone in a reverse bow and arrow leg stance. A typical bow and arrow leg stance is used for stability in the front-back direction. It will have both feet positioned at an angle, with the front leg bent and the back leg out straight. The front knee is turned in and the toes on both feet are pointing in the direction of the knees, parallel to each other. Weight will be distributed 70% on the front (bent) leg and 30% on the rear (straight) leg. The practitioner will be facing forward. The reversed variant of this stance will have the weight distributed the other way: the rear leg is bent with 70% of the weight and the front leg is out straight with 30% of the weight. Often, the reverse version of the stance is used in transition while stepping or preparation for a technique (such as a sweep or a kick).
The right arm is executing a low circular block. These are typically used to deflect low punches or kicks, or other incoming attacks. It is likely that the person in this diagram either is mid-turn, defending against an attacker striking from behind, based on the body position.
The left arm is executing an upper block. These blocks will typically be used to defend against high incoming attacks striking in a downward motion. They can also be used to deflect attacks to the face or break out of shoulder or lapel grabs.
The positioning of the person in this diagram makes me think that this is the likely situation that it is illustrating:
The practitioner is engaged against a person in front of them, and is in a bow and arrow leg stance at the time (he could have transitioned to it from executing a strike, or other technique, or it could be his "ready" stance). The attacker executes an upper attack or grapple and is deflected via the upper block. At the same time, another attacker advances from behind and attempts to attack the practitioner with a mid-range kick to the kidney or floating ribs. He turns and deflects this incoming attack while still maintaining control of the first attacker's arm.
Of course there are other situations where this position may end up occurring. However, this is what immediately occurred to me when looking at the diagram.
