HDTV-ready can be very misleading, as it sometimes means the set can accept an HD signal, but it doesn't mean the set shows all 2 megapixels of full-HD picture resolution. Some "HDTV ready" TVs may actually discard most of the full-HD resolution and display an image that has been downscaled to standard definition.Read on over at Business Week.
An HDTV set with integrated tuner usually means it shows an image with around 1 megapixel of picture detail at 1366 x 768 (pixels, horizontal x vertical) or 1280 x 720. And full HDTV usually refers to a TV that can display the entire 1920 x 1080 resolution of full HD content without throwing any detail away.
What's HDTV and its different flavors

Still wondering about what HDTV is and what all the differences are? Check out this article and you'll learn lots more about it.