Assets/collider.cs(4,14): error CS0101: The namespace `global::' already contains a definition for `PlayerController'

I am designing a low-level game for a school function as well as to gain experience for my future career. i was attempting to make objects in the game collectibles, and upon entering the script i was given to use in an example video, this error started to pop up.

PlayerController is already a Unity class, you can’t make one of the same name.

Change the name of your PlayerController class. That should fix the problem.