Pro Creep Killing

I'm not exactly new, but I'm not exactly a veteran either. As you will probably be able to tell form my query.
I was watching the International, and it left me wondering why they would kill the creeps in the method of -- Attack,turn away,attack,turn away... You get the point. Now, I know about orb walking, but most of the heroes used weren't "walkers" and weren't using walking items. So... HUH?

There's a thing called Backswing animation which is a part of attack animation. You may have noticed different heroes attack with different animations - for example, Lina has very long animation while Morphling has pretty quick animation. The animation consists of pre-attack animation(like a hero raising his sword to attack), attack itself(when the damage is dealt, or projectile is created) and Backswing(animation that goes after the actual attack). This backswing animation can be canceled for a minor increase in effective attack speed.

http://dota2.gamepedia.com/Backswing <-article

Though I do not know if I understood you correctly, fix me if I'm wrong.

No, you got it. And that kinda what I figured was happening, just can't see the advantage in doing that with heroes like viper or sniper (or anyother "iper"). Heroes without those long animations. I would think that the gain is very minimal at best. But, I guess at that level of play any advantage is welcomed.

It's just a habit, I suppose, when you do that while playing the likes of Sniper or Gyrocopter. And that attack-turn away thing is more of a rhytm setting thing than actual cancel of animation. Many players prefer to constantly click around their her to be in constant movement and to set a rhythm if they will have to react fast on something - that way they are less exposed to things like Sacred Arrow, or can faster react on someone's Blink. Attacking a creep and waiting for an animation to end disrupts that rhythm and hero stands still for a split second which can sometimes be the difference between life and death.

Then are they just clicking away for the target, or are they hitting the cancel button, or both?

Clicking away. If they would manually cancel the animation, they would stand in place for a minor time, not turn away.

Now correct me if i wrong here (going to try mechanics of dota again), but you don't actually attack fast by doing this, because the delay between attacks is still the same. HOWEVER what this is great for is when you are chasing heros, because you spend less time in your animation and more time running letting you get 1 or 2 more hits on. It makes you more efficient but not attack faster.

Oh wait, I have messed up the articles, here's the relevant one(http://dota2.gamepedia.com/Attack_animation).

Yes, you're right about canceling not increasing your AS, but letting you issue other commands quicker.

It's also good practice to keep your hero moving at all times really, to avoid skillshot initiations.

It's often seen when attacking towers.

I do it partly for the reasons above, partly because my hero being still annoys me