The "Ranger Choke Hold" that Al Pacino does in "The Scent of a Woman" , is it real?.?

That is a version of what is called a front lapel choke in martial arts like Judo and ju-jitsu. In those martial arts you reach across grabbing your opponent's opposite lapel with each hand. Your hand on top though you bend your wrist forcing that bend in between the columns of muscle that run up and down your neck against the larynx which sits recessed slightly in between those columns while also pulling your adversary into that bend to apply pressure by flexing both your wrists. This allows you to use leverage rather than relying on raw or sheer strength.

The way it is being applied here is because the guy is wearing a t-shirt and instead of using the bend of the wrist against the larynx he is grabbing the windpipe and you can definitely hurt someone this way as well.

He just balled up his shirt and "grabbed" (lightly, I might say) the sides of his neck. I mean, grabbing someone by the throat can choke them, but he didn't really do anything special there.

You were in the military 13 years and have not figured out that movies are not reality? They are choreographed for entertainment. The fights are not documentations of real fights, let alone martial arts.