Google Hangouts has long since offered the ability to share a screen through a video chat. However, this new feature allows you to select what you want to share over your video Hangout. Google cast does not need to be installed to use this feature.
This is a great tool for presenting information via video conferencing.
For More Information: http://googleappsupdates.blogspot.com/2016/08/introducing-casting-into-hangouts.html