A spring holds the vehicle up and allows the suspension to move so ride quality is better than a lawn mower.
A shock is a dampener - or a device that prevents a vehicle from simply bouncing up and down the road uncontrollably.
On a 3rd gen, it uses coil springs at all 4 corners - front and rear.
In the rear, the spring is between the body/frame and axle. If you remove the rear shocks, the truck just sits there and smiles. The shocks are only there to dampen the springs.
In the front, the spring is captured at both ends by the shock. This is called a coil over spring. The shock is called a strut because it acts as a structural member of the vehicle. The front end would collapse with out this being mounted as a team between the lower suspension A-arm and frame.
Generally, when people refer to a coil over, I assume they are referring to a pre-assembled strut and spring combo.
Hope this helps.
Stephen