Question: I was just curious as to what exactly Sprite Kit Restitution actually configures? I know that it configures some behavior about an SKPhysicsBody's parameters, but how does the behavior differ?

Answer: 
Sprite Kit Physicsbody Restitution is defined as

> 
> "a property describing how much energy a body retains when it bounces 
>  off of another body, basically a fancy way of saying "bounciness""
>  -IOS Games by Tutorials
> 
> 
> 

Also an [excerpt from the IOS Developer Library (Apple Docs)](https://developer.apple.com/library/ios/documentation/SpriteKit/Reference/SKPhysicsBody_Ref/Reference/Reference.html#//apple_ref/occ/instp/SKPhysicsBody/restitution)

> 
> This property is used to determine how much energy the physics body 
>  loses when it bounces off another object. 
>  The property must be a value between 0.0 and 1.0. The default value is 0.2.
> 
> 
> 

Also just note that the compiler won't complain if you supply values outside of the range from (0.0 to 1.0); however, think about what it will mean to have a value greater than 1, for example. The body would actually end a collision with MORE energy than it had initially. That's not very realistic behavior and often times will very quickly break your physics simulation.
Restitution set the bounce of an object, if you set it to 1.0f, the collision will be bounce back with the same force to the impact. If you set it to 0.0f if won't bounce at all.