The Ethernet cable goes directly from your router (plugs into the router) to the TV. You need a Ethernet outlet on the back of the TV to plug the other side into. Newer TV’s have them. It delivers the fastest internet speed you can get from your system. No WIFI needed.
You will eliminate buffering with an Ethernet cable.
You can also use ethernet cables to plug directly into your computer making it faster.
The more devices you have on Ethernet cables the better your WiFi will be as there are less devices using WiFi. So, your phone and tablets should work faster.
Ethernet cables should also be run to appropriate locations when building - same as electric. But obviously you can run Ethernet cables anytime same as other wires.
Ethernet cables are also referred to as CAT5 or CAT6.
MoKelly
Switching to ethernet is likely to have zero affect on the buffering. Most buffering is caused by your ISP limitations, not your home network. The reality is that wifi has improved so much that ethernet is now the exception versus the rule for internet.