High definition is really confusing, help appreciated

[akishore]

Sorry if something similar has been posted before, I didn't find anything good with search.

I'm trying to understand HD stuff since I'm interested in buying a TV and think I should get an HDTV (good long-term investment?). But it's ultra-confusing:

1. HDTV vs HD-ready TV vs HD-capable TV. What are the differences?? I think I vaguely understand that the latter two mean I still have to buy some other gizmos (HD tuners??) in order to see HD television (e.g. ESPNHD), but I'm not sure.

2. What part of the TV makes it HD? Is it JUST in the inputs? If so, what inputs matter -- HDMI? What about component inputs, are those HD?

3. A concrete example is this Dell LCD monitor. It doesn't mention "HD" anywhere in the description or specs, but suppose I plug in an Xbox 360 or a PS3 (both HD consoles) -- will this monitor indeed show high definition video? EDIT: I ask because one review mentions "I love that this monitor is HD ready".

Thanks in advance.