Delete all photos from iPhoto albums and iPhoto Library?

Photos has two commands to remove Photos - remove from album and delete from library. It will depend on where you are selecting the photos for deletion, what will happen when you use delete key ⌫:

• When you are deleting photos from an album you created yourself:
  • The delete key ⌫ will be mapped to "remove from album" - the photos will be removed from the album, where you selected them, but but keep them in the library, when you are selecting photo in an album. The delete command will not even appear in the Image menu in some older versions of macOS, only" remove from album".
  • Holding down the command key ⌘ while pressing ⌫ will bind the key to "delete image" and move the image to Recently Deleted.
• When deleing from the Library views - All Photos, Days, etc, the ⌫ key alone will suffice to move the photo to Recently Deleted. Holding down the ⌘ key as well will suppress the promo, if you really want to delete the selected items.

To delete the photos permanently, select them in Recently Deleted, inspect them, if you accidentally deleted more items than you wanted, then delete them there. This will permanently delete them, without any option to recover them.

If you upgrade upgrade to macOS 13, both the commands "remove from album" and "delete Photo" will be back in the "Image" menu and in the contextual menu (ctrl-clicking a photo), when you select the photo in an album. It is one of the improvements in macOS 13 Monterey.

Do you mean iPhoto or Photos? iPhotos hasn't been supported for years. I'll tell you about Photos, and I think I remember that it was similar in iPhoto

Albums don't have pictures in them-- they have lists of pictures from the Library. That way Aunt Bertha at the Grand Canyon can be both in the album labeled "Aunt Bertha" and in the album labeled "Grand Canyon." Hitting Delete removes that picture from the list, but doesn't change the picture.

The Library view shows all the pictures in the Library. You can select all of those and use command-delete to delete them all-- they'll be removed from all the albums, their names can't be there any more.

EXCEPT-- there's a special album called Recently Deleted. All the pictures you deleted are still in there! They go away permanently in 30 days. But, you can select them all and delete them and be rid of them forever.

Alternatively, you can find the Photos Library, drag it to the trash, and empty the trash.

You're not.

Select the album. Go command-a to select all the images. Right click on any one of them and choose Delete'