Adwords call metrics are a new feature from Google that automatically includes a unique phone number in your ads, allowing you to measure the calls you receive from Adwords.
Prior to this, the use of third party software or an additional phone line were a way of tracking phone calls received from your Adwords advertising campaign.
This new feature from Adwords makes it easier than ever to measure phone calls that your Adwords campaign has generated for your business.
Using the technology behind Google Voice, call metrics makes your unique phone number clickable on both desktop and high-end mobile devices.
When a user calls the number displayed in your ad, the call is routed to your business while Adwords keeps a track of the call that takes place. Afterwards you can see the number of calls generated by each campaign in Adwords.
With this information you can better refine your marketing strategy to make sure you're getting the most out of your ads. Currently, call metrics is only available to a selected few US advertisers.