Knitting Theory: wrap and turn and short rows!

I'm making progressions in the Miss Bennet Puffed sleeves sweater and I've passed the most critical point of the pattern, the wrap and turn part.

At the beginning I could not understand why that technique was used and how to do it, but now that I've been going trought it I can say that not only it's quite easy, but is even quite useful to shape the knitting projects and make them fit better.

Wrap and turn is used in two cases: to change direction to your knitting or to make short rows.

In example, I'm knitting my row, but I don't want ( for any reason) arrive at the end of the row, what I have to do is turn the work and start knitting in the other direction. Simply turn it!

Now, if I'm knitting, after turning it,  probably I would start purling and vice versa.
As I'm in the middle of my work and not at the edge, it's not nice to simply turn, it would make a little hole.
What should I do to avoid the hole? I arrive at the point where I want to turn and I pass the yarn wrapping the next stitch in raw waiting to be knitted.
How can I do it in an easy way? I have to pay attention to the position of the yarn while I'm knitting, that is in the back of the work, and to the final position of the yarn when I've turned it and I have to start working again in purl stitch, that is in the front of the turned work.
So, to do it without the hole I have to pass a round of yarn around the stitch not worked.

I don't know if my explanation is clear, anyway I've found this video on you tube by Cotton and Cloud that is very clear:

It teaches  even how to pick up the wrapped stitch when working again that stitch.

But while learning wrap and turn, another question came in my mind, and it is, why inserting short rows in my work? The answer I could find is that short rows add turns to the work and make it fit better.  They make knitted triangles. In example you make short rows in the back of a sock to make room for the heel of the foot; in a sweater you can make room for a breast or a gluteus that needs it. It makes the difference between wearing a sack form clothe and a shaped one.

In my humble opinion, the best explanation on the use of short rows is the following, by knitpics: