When a product is newly created on Amazon, it receives its own ASIN. ASINs are only used on Amazon, and are closely tied to the UPC/GTIN/EAN barcodes that are used in worldwide retail.
Amazon allows sellers to create ASINs without providing UPCs through brand registry, but yes usually an ASIN is deeply associated with a given UPC unless that ASIN is merged with other(s) at a later date.
When a product is newly created on Amazon, it receives its own ASIN. ASINs are only used on Amazon, and are closely tied to the UPC/GTIN/EAN barcodes that are used in worldwide retail.