Yves heard that the custom_label attributes can help him organize his Shopping campaign. With custom labels, Yves can provide any value he chooses so he can organize his campaign by his own goals

Explanation: 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