The basics of the kinetic chain lie in the axis created by your back foot, knee, hip shoulder, hands and head. While I'm not going to get in the traditional "Linear vs. Rotational" hitting debate, here's what I will break down for you.
Hitting is a constant redirection of energy from the ground through the body and ultimately into the baseball. As a hitter begins his/her swing with a controlled stride, the hands will drop the bat into a hitting slot (Right handed batter), and starting with the back (right) foot, begins the swing.
Beginning with the "squish the bug" (for lack of a better term) movement with the right foot, the kinetic chain begins. The foot drives the right knee, which drives the right hip, which drives the right shoulder, which drives the hands and ultimately the bat through the hitting zone. The front shoulder and hip open enough to allow the bat and hands to move explosively through the hitting zone while the front leg remains firm (not necessarily locked out) but FIRM to help redirect energy from the driving legs into the upper body.