Let us see the effects of SHAREN and STRUCTURE on real photos.
Please watch them while comparing both effects carefully. Light gray line effect appears at the edge on SHARPEN result. The brightness level of dark area around edge such as shadows is darker on STRUCTURE result.
Example 1. CHARACTERS



Example 2. HAIR STRANDS



Example 3. FOODS



Example 4. FIGURES



Example 5. Golden Buddhist Statue



SUMMARY
Can you see the difference clearly? Let us summarize the sharpness functions. From left to right: the original photo, STRUCTURE result, SHARPEN result.

You can see clear photos on both SHARPEN and STRUCTURE results. STRUCTURE lowered the brightness of dark colors such as shadows as a result the photo have a contrast. SHARPEN adds light gray line effect as a result, the photo became shinier such as shine on the mask.
Let us summarize the Sharpness functions.
SHARPEN
It makes your photo shinier
STRUCTURE
It makes your photo clearer and produces a contrast
I explained the difference between SHARPEN and STRUCTURE. However, in reality we need to improve our photos using both functions. Please see below.
This is a Ginger Ale with Samurai design photo


You can see the Samurai clearly on SHARPEN & STRUCTURE result because of the powerful contrast around edges. There is a big difference between black color background and light gray outline of the Samurai. STRUCTURE lowered the brightness of black color more and SHARPEN added light gray line effect at the boundary of the Samurai. As a result, we can see clear edges at the boundary of Samurai and see whole photo clearly.
You can see the powerful improvement. SHARPEN increases shininess around edges. In contrast, STRUCRURE darken around edges. They implement each other and produce a big gap in brightness level around edges.
Hope you can understand Sharpness deeply.

I will give you the effective ways to improve your photo using both SHARPEN and STRUCTURE in my blog. Click #Sharpness in my blog. So you can see the examples.
Enjoy!