Windows users can share their entire desktop, including all of the active/enabled monitors, or can choose to share specific applications* on any of the monitors.
This feature is great for collaborative environments where developers, architects or engineers want to share or collaborate in a high resolution or multi-monitor environment.

Make sure to only share specific applications* if you do not really need to share everything on all of the desktops/monitors.
This will improve performance by sending less data and also reduce the amount of scrolling for the single-monitor guests, both of which improves their experience in your meetings.

For more information on application sharing on a Windows computer, please see this article.

*Windows computers only. Mac application sharing will be available in the future.

Macintosh users can currently only share the entire desktop of the Primary monitor, regardless of how many monitors are active/enabled on the Mac.
Multi-monitor support and application sharing will be available in the future for Macintosh users.