What's the use?
This catalog allows you to send price updates, availability, more frequently than a Google Local products feed.
It is useful for the LIA program (Local Inventory Ads).
It indicates to Google the quantity of products that is available within each store.
Note that Google only display products with a stock higher or equal to 5 units.
How to use this option?
It has to used along with other feeds from the LIA program (Local Inventory Ads).
Its setting is similar to Google Shopping channel.
This feed is working through CSV and has to be registered in your Merchant Center.
To know more about its use within Google, please consult their help center.