What does this box actually do?

I already have a smart TV but cannot connect it to the Internet as I need some sort of special cable for my Panasonic Smart VIERA TX-P42ST30B, but I can connect to the Internet via my sky box, but as I only have one single feed I do not know what is the advantage in being connected to my broadband via the Skybox.

So wondered what the Sky NowTV box would offer me.

I was thinking of getting a Chromecast box for the same reasons but again don't really understand what these boxes would actually give me over what I already have.

Can you give me some advice please?