Yves heard that the custom_label attributes can help him organize his Shopping campaign. With custom labels, Yves can provide:
Google product categories so he can organize his campaign by different categories
any value he chooses so he can organize his campaign by his own goals
the product’s condition so he can organize his campaign by new, used, or refurbished products
the brand of his product so he can organize his campaign by different brands
Label that you assign to a product to help organize bidding and reporting in Shopping campaigns are called custom_label. You can use up to 5 custom labels and 1,000 unique values per product for each custom label across your Merchant Center account.
Read more here: https://support.google.com/merchants/answer/7052112