Share or Export images from Mail to Photos

If I get an image in Mail and want to save it to Photos, there are a number of options. I can just save it to the desktop and take it from there to Photos. I can also use the Export to Photos function, or I can use Share>Add to Photos. Why are there the latter two options in the shortcut menu? What is the difference? As far as I can tell the Export function keeps the metadata, while the Share function loses it, otherwise the images seems the same. What is the point of the Share function other than to create confusion?

Thanks very much for any guidance.