does my vizio hdtv tv "46inches" need a HDTV cable to display the channels and stuff in high defenition?

of course.....you need HDMI or DVI digital signals to get HD images.

if you just have a normal dvd player, you can't get HD.you'll be watching movies in 420p..get a blu ray disk player or a HD-DVD player to get a full hd 1080p image

The Vizio includes the tuner, so if you connect to a high definition digital signal from an antenna or cable, then you will get HDTV.

If the cable box or DVD player is not high-definition, then you will need to upgrade those.

Probably, you need a wire to go from the cable box to the TV. What kind of wire depends on the cable box. Probably, its a standard RF cable (the kind that comes out of the wall). Make sure it's a good quality cable though. Then, plug that RF cable from cable box to the DTV/TV input on the Vizio.

Then, get wires for the DVD player. It depends on what kind of DVD player. For a standard DVD player (not hi-def), look for something called component video on the back of the player. Then, get component video cables and connect from the DVD player to the component video input on the Vizio (I think its the purple section). Be sure to connect the audio wire as well, since the component video cable wires are just for video.

On the Vizio, use the [AV] button on the remote to switch from TV to AV1 (which should be your dvd player).

depends.. if you are simply using an antenna to catch local Over-the-air broadcasts, then your tv may include a HDTV tuner (check your manual), and if that is the case, all you need is an antenna.

if you are connecting to a cable box, you will need to insure you subscribe to HDTV content through your cable provider, and then you will need either a HDMI, DVI, or Component video cable set up depending on what type of output the cable box supports. I listed them from best to better.