Natural or existing shadow
As the term suggests, the natural shadow is keeping the originality of the image and putting nothing artificial in it. But when you remove the background during editing, it will remove the shadow that occurred with the picture naturally. To get it back, an image editor creates it manually and optimizes the opacity and transparency to give it a realistic appearance.
Reflection or floating shadow
We apply it when we want to create a feel that the product is placed on a clean surface such as glass. In this effect, we see a reflection of the product as if we are seeing the product in a mirror. We can use this technique for displaying jewelry, watch, and any other products that are displayed on glass or clean counter.
Drop shadow gives a realistic impression of the image that it feels like the object is floating above the shadow behind it. It is a unique shadow technique that portrays a view as if the product is under direct sunlight from the top. For showcasing eCommerce products, it is the best shadow effect compared to other techniques.
When we cast light on an object, we see a slanted shadow falls behind it. We call it cast-away shadow. During creating a more natural shadow of a human being or a large object, applying this effect is more practical. In Photoshop, we can add a castaway when the object is touching the surface.