What exactly does "Ethernet-capable HDMI cable" mean?
No it does not mean you can do anything wirelessly - it is a cable - and it isn't likely to help you stream anything to it either, unless you have a requirement for HDMI devices to share a network connection.

Version 1.4 of the HDMI standard allows for 100Mb ethernet to be transmitted along the cable between to HDMI 1.4 capable devices.

Check out the HDMI wikipedia page for some basic info