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: 
Restitution basically equates to an object's "bounciness"
The **restitution** , in Sprite-kit as in real life, is a value that can be obtained by dividing the relative velocity between two objects after the collision with the relative speed between the two objects before the collision

```
e = relative speed after collision / relative speed before collision

```

This value is able to let us know the level of bounce or elasticity of the collision.

We can distinguish three specific situations that differentiate this value.

* The first when there is no dispersion of kinetic energy, we can also call
this situation as a "perfectly elastic collision" where there is a
very high percentage of rebound, and we can measure the restitution with
the value **e = 1**
* The second happen when the maximum movement (kinetic energy) is lost
completely, then we have "an inelastic collision" where colliding
objects remain stuck and move together. The value **e = 0**
* The last case concerns the majority of collisions or all those
situations in which the value is **e between 0 and 1**, or in the
middle. It is essentially an inelastic collision, where a bit of
kinetic energy is dispersed. In fact the Sprite-kit `physicsBody` restitution **default** value is **0.2**