Which one is the delete button on an Apple keyboard?
A detailed description on this is available on this post https://superuser.com/questions/482771/difference-between-cmdbackspace-and-fnbackspace-keyboard-shortcuts-in-osx
To summarize:

The most commonly used key for deleting elements that can be selected in the user interface is Backward Delete ⌫ since it's available without a modifier on all Apple keyboards. This applies to songs on a playlist, graphics in an image editor, deleting text boxes in Pages, etc.

The Forward Delete fn⌫ is mostly used for the same actions, so you can actually use both in an interchangable way for most applications, be it Numbers, Excel, iTunes, Photoshop, etc.

The combination ⌘⌫ is intended for actions that might have an immediate (unwanted) effect. One could indeed map trashing files and folders to a simple ⌫, but this could lead to accidental deletions. Finder uses the modifier as a safeguard. This also explains why iTunes will only delete a song without confirmation if you press the ⌘ modifier.