Working with Collision Layers in Unity

Objective: How to set-up and use Collision Layers on the Unity Engine.

What’s a Collision Layer?

Collision layers are a concept used by physics engines to decide which objects should collide with which other objects. — eZEngine

This is how the Collision Layer matrix looks. Inside the red square I specify the intersection of two layers: Enemy and Player.

If we create to different gameObjects with a RigidBody and a Collider attached they will trigger each other.

Go to Edit > Project Settings to see the Collision Matrix.