Without going into the technical details, suffice to say that my receiver is now connected to my home network router, which allows me to use my Samsung phone and iPad as remote controls. It is also supposed to allow me to access internet radio, but I have not been able to get it running yet.(19/Jun/13 update: my Net Radio is working now! It has something to do with the network connection)
Of course I can now properly connect my plasma TV to the receiver to make full use of my 5.1 surround sound speaker system for TV, thanks to the available optical cable feeding audio back to the receiver.
HDMI allows me to connect my Blu-Ray player to the receiver for better video output than the ancient composite video RCA connector.
USB port allows me to plug a USB stick into the receiver. My entire collection of MP3 music can reside in one 32-GB thumb drive. My Android app can remotely switch on the receiver and play any song from my collection .
Sound quality on the Yamaha RX-V473 is as good as the reviews say. Not exactly an audiophile myself, I must say the sound system is as good as I can ever tell. My system as it stands now consists of the amplifier receiver as the hub, 5.1 speaker system, TV, and Blu-Ray player. I am so blessed!
(Note: Smart TV is another way to get LAN connectivity. Multi-HDMI ports in the TV can also provide for various game consoles and disc players, like what the receiver does. However, it is doubtful that any TV manufacturer will incorporate a high end sound system into even a high-end TV, for cost reasons. Hence the need for an AV receiver if you are after a more satisfying home theater experience.)