Effectively your TV just becomes a dumb screen, the television does nothing except display what is input from the HDMI dongle. The TV will be set to "HDMI" input, just as if you'd connected a Bluray player etc.
The HDMI dongle comes with its own remote control which just controls the dongle. Volume control will likely still be on the television remote. If you want to view normal television again you just change the TV back to "TV" mode in the AV menu.