What it is:
When you enable a Location Extension, you can choose to show the address of your business location that is closest to the customer and also include a local phone number. Better yet, if the customer is viewing your ad on a smartphone, they can click that number to give you a call.
A particularly powerful feature of Location Extensions is that the address shown to the customer is typically the business location that is closest to them. If you have multiple business locations set up for your campaign, Bing Ads will display the address and phone number for the location that is closest to the customer. The radius for the location display is about 50 miles. If you don't have a business location entered that is within 50 miles of the customer, no location will be shown in your ad.
Locations that you create apply to all your campaigns within a particular Customer ID. Also, note that you enable Location Extensions at the campaign level and they get applied to all ad groups and ads in the campaign.
All Bing markets
You can easily add an ad extension to multiple campaigns or ad groups with a few simple clicks.
If you have multiple locations for business, Locatino Extensions will show the nearest business location within 50 miles (80 kilometers) or the value selected for radius targeting.
Here are the details for the Location Extensions account limits.