WIDI means WIreless DIsplay
Widi is a technology from Intel and can connect devices wirelessly with a display, it is a techiek that is based on WiFi. One advantage of WiDi is that it uses existing hardware. Since you have to pair devices with a pin (like BlueTooth) it is quite easy to use. WiDi also has some limitations: it is not possible to stream protected (DRM) movies to a television and it is prone to malfunction. The WiDi technique has been integrated into televisions and computers since 2012.
Intel explains WiDi [YouTube] VT842FQCgNI [/youtube]