Yes, it is for streaming your display to a Miracast compatible TV, etc.
From Nexus site:
Some of this information applies only to devices running Android 4.4.
Nexus 4, Nexus 5, Nexus 7 (2013), Nexus 10, and HTC One Google Play edition are compatible with devices that support the Wi-Fi Certified Miracast™ protocol for wireless display. To turn on the wireless display feature, go to SNP_BEE8810A5FCD80173673B4B15A1804EAEE99_3529219_e n_v0Settings > Device > Display > Cast screen > SNP_2918040_en_v1 Menu, then check the box next to “Enable Wireless Display.”
You can cast the screen to wirelessly stream video and audio to a variety of displays and other devices that support Miracast - even when a standard Wi-Fi network isn’t available. For example, you can cast the screen to show your device’s screen on a TV equipped with a certified Miracast adapter.
For more information, see the documentation that comes with the Miracast-certified device you wish to use with your tablet or phone.