Hello,
Variable Product is the nature of the Product defined from WooCommerce end, where you can define multiple Attributes in a Single Product and then use them to create Variations under a Product and sell them separately for a Single Product.
Whereas, the Linked Variations is a feature of the WoodMart Theme where you can link different Simple Products through a Single Attribute i.e. you can create separate simple products and group them into one bundle by a common attribute.
You can read more about them here on the following Guides:
https://xtemos.com/docs-topic/linked-variations/
https://woocommerce.com/document/managing-products/#adding-a-variable-product
Hope this helps !
Best Regards.
.
