Unable to rearrange Photos in an album on iPhone

People say they cannot rearrange their photos. I thought I couldn’t either when I tried rearranging them. I was however in the photos part that contain all your photos/videos in your phone. When I tried to move a photo it would simply return to its original position. It was only when I was in an album I had created was I successful in moving a photo to another location within the same album by selecting the photo, ‘holding’ it and then by dragging it to the new location and releasing it.

[Re-Titled by Moderator]