If you have a compatible Mac and iPhone and they are properly set up for Continuity, you can start a phone call from a Safari page with a single click.
All you need to do is click and drag to highlight a phone number on a page (such as a business or Yelp listing), and a box appears around it with an action arrow. Simply click that arrow, then click “Call using iPhone.”
As long as your iPhone is within Bluetooth range (around 30 feet, but ideally less), FaceTime will open and start the call. The call actually goes through your Phone, but your Mac effectively works as a giant Bluetooth speakerphone; all dialog works through your Mac’s built-in speakers and microphone.