"Traditional" aiming is point of aim corresponding to point of impact. This technique works with handguns out to about 50 yards (depending on gun/sights/ammo/shooter), and to varying degrees with rifles depending on zero distance and required degree of precision.
With rifles, if all you need to do is hit somewhere on a human sized target from muzzle to 350 meters, just hold in the torso and blast away (depending on zero distance). However, if increased levels of precision are needed, the shooter needs to understand his trajectory, especially at close range. This is due to the level of precision needed to consistently place rounds into the critial structures of the threat on demand, under stress.
In these situations, if the shooter is using a 100 meter zero, he simply places his point of aim 1.5 inches above his needed point of impact and he will hit within a 3" circle from 3 meters to 70 meters. The user can fine tune his holds for greater precision by holding approximately 2.3 inches above the needed point of impact from 3 to 25 meters, and then reduce that hold to 1.3 inches above center from 25 to 55 meters, and simply hold directly on what he wants to hit from 55 to 175 meters.
See the "Zen of the 100 Meter Zero" sticky for more info and discussion here:
https://www.m4carbine.net/showthread.php?t=107572
The alternate method is for sighting devices that have a distinct point in the reticle or sight that can be used for rapid aiming. For example, the bottom of the 65 MOA ring in the EoTech line of sights, a thick outer crosshair or circle in traditional scopes, or the base of the front sight of traditional iron sights. At close range, these excessively lowered aiming points will provide point of aim/point of impact at a specific close range, and will be "close enough" for high levels of precision within a narrow window of employment. The problem is that once that narrow window is exceeded or reduced, the shooter will once again need to apply a hold-over/under, which makes the whole purpopse of modern zeroing methods moot. It also forces the shooter to accurately estimate distance to within single digit meters/yards at distances that require immediate action/reaction to win.
So, my advice is to learn your "large window" holds, and train yourself to apply them, so that when you need it, it will be habitual and intuitive.