Dynamic Posture - Basic Pivot
This is the basic concept of being able to maintain your body angles through the swing; The topic is fundamental of playing the game and can be much more complex. Much more information on how we turn and typical patterns can be found in the biomechanics section.
If you like 'basic' then we are aiming to rotate the shoulders/torso to 90 degrees in the backswing while holding the leg action to a minimum (without creating huge tension). Our head needs to stay relatively still, resisting any lateral or vertical movement.
A common mistake I see with students is to turn the shoulders to the max in the backswing in a belief that this will create more distance. There are a number of reasons as to why this is not the case. Your best chance of creating power is to make a well sequenced and balanced downswing. To this aim, rotate your torso between 80-95 degrees for your best chance of making a coordinated powerful downswing.