Hello Adesh,
Let's say a product has 3 variants.
When
Show variants as options to the main product option is selected, In frontend (list views) you will see the main product only. You can view the available variants on the product details page as options to the main product.
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If
Enabled and Show each variant as a separate product is selected, you can see the variant on the product details page as options as well as in the product list views.
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I hope this helps.
Thank you