Roland's answer covers some bases, with a few critical omissions:
- Pushing the body of the opponent away after a definitive stroke, to clear the space
Fundamentally, you don't want the opponent falling in a way that could tangle up your legs.
You see this mostly clearly when the forms are practiced in the Wudang, as opposed to contemporary external style, because Wudang is typically demonstrated in a less phrenetic manner than contemporary wushu, more consistent with conflict where there is a chance of instantaneous death.
The techniques derive from the use of the system for individual dueling and multi-opponent combat.
If you analyze certain cuts, you will see the push emerges just as the cut finishes. An example is a classic uppercut that ends with the sword fingers extended forward and the blade in a high guard position, sword wrist over head.
You see it most clearly in Wudang because wudang fencing "invites" the opponent's blade, letting it get very close to the body, such that the famous "drawing" cuts, side to side or upward, are applied from inside the guard, at face-to-face range.
It probably continues to exist in the practice because Chinese fencing in an extant system, not reconstructed. (About 4 generations back from the teachers of my generation, there was still some dueling going on.)
- Striking the opponent from inside the guard
Fist can be used in place of sword fingers to make such a strike, but this overlooks the goal and function—the poke is ideal because all you're looking to do get the opponent to react (wince) slightly to create an opening to insert the sword.
Obviously, you need to be controlling the opponent's blade with your blade before attempting an off-hand strike.
You will notice that in many of these moves, the blade is in a guard position, for instance, drawn back and protecting the thigh. Here, this sword position connotes a successful counter, controlling the opponent's blade by having parried it off-line, and "sticking" to it while making the finger strike.
- Wiping the blood off the blade
Few practitioners seem to demonstrate this, but I always do—it shows a higher level of skill, and would have had a practical use on the battlefield. Even using gloves, blood on the handle makes it first slick, then stick, neither optimal for fencing, because both conditions inhibit the blade's action.
I mention this last one because the end of the movement leaves the sword fingers extended ahead of the sword's point.
Typically, but not exclusively, sword fingers forward, pointing up connote a push, and sword fingers pointing forward connote a finger strike
Again, finger strikes don't need to be hard, just draw the opponent's attention for an instant.
"Wiping the blood" typically ends with the sword fingers pointed inward, in the position used to draw them along the flat of the blade, away from the crossguard. (You also see this "inward" orientation at the beginning or end of forms, where a push to the side is generally optimal with the palm out, thumbs down, as practiced in bagua. "Inward" sword fingers also connotes blocking/countering with the off-hand.)
As my teacher used to say "If it doesn't have a martial function, it's not martial art."
Good forms contain no techniques that do not have at least one martial function.