You can use campaign priority to:
edit maximum CPC bids, tracking templates, or custom parameters and destination URLs for non-subdivided product groups
promote certain product groups across all your campaigns
determine which campaign’s bid to use for a product when the same product is included in multiple campaigns
subdivide campaign products according to freely-assigned values with custom labels
Explanation:
When you have the same product in multiple Shopping campaigns, you can determine which campaign should participate in the auction for that product with campaign priority. Your campaigns already have a priority: Low. But you can change this priority to Medium or High. These priorities determine the bid for any product that the campaigns share.
Read more here: https://support.google.com/adwords/answer/6275296?hl=en