What does it mean when it says enable desktop notifications?
If you're using either Chrome, Firefox, or Safari as your browser, you can enable desktop notifications. While enabled, a notification will appear whenever a new email message arrives in your inbox as long as you have Gmail open in a browser tab.
What do desktop notifications do?
Desktop notifications create a popup message each time an inbound call is received. Popup messages provide both a visual and audio notification of an inbound call and appear even when the browser is minimized.