Miracast is the technology Microsoft uses in Windows to wirelessly push your screen and audio to a remote screen or monitor. To make it work, you need a wireless receiver attached to the remote screen. I use two different options: the Microsoft Wireless Display Adapter and the NETGEAR Push2TV PTV3000. But I've also heard that the Actiontec ScreenBeam is a solid contender and I plan on testing that soon.
It's hard for me to believe, but it took almost an entire month after the launch of the Windows 10 upgrade to sit down to use Miracast again. Prior to the launch, I would use it almost daily. But, alas, things have been extra busy as of late, mostly due to a bunch of travel. So, it took me a bit to figure out where Microsoft has placed this feature. I'm a bit ashamed that it took as long as it did.
In Windows 8.1 you'd choose to "Project my screen" through the Charms menu. In Windows 10, all device connection actions, including projecting your screen, is now part of the Connect setting.
To get to it quickly, just tap of click the Action Center and locate the Connect button.