Product information. Things like "The mainboard named XY from producer ABC has the manufacturer sku 1234567, the EAN-13 00123... and the UPC 01234...". Ideally add to that the custom specs, like "it has that many usb slots and this socket" etc. But I think I miss part of the picture here, there is probably a channel transmitting structured information like this from manufacturers to vendors, I just never found it.
My startup Semantics3 works on this problem - https://semantics3.com/
We have a standardized taxonomy and ontology to which we map all our products to. It's a garbage in garbage out problem but as long as the product has the information in some sort of semi-structured or unstructured form, we typically can infer attributes and standardize them based on their ontology (i.e. They have 4 USB ports)