“ATSC” means “Advanced Television Systems Committee” which is the group that set the standards for digital broadcasting in the U.S. These standards include high definition and standard defintion (HD and SD) formats. For consumers, ATSC is used to refer to the digital tuner in a set, e.g. “this set has an ATSC tuner”. That means the set can receive digital broadcasts, but does not necessarily mean HD. However, for all practical purposes, any HD set that has an ATSC tuner receives HD programming.

“HD Tuner” is an ATSC tuner that will receive the HD part of ATSC standards. As I said above, all HDTV sets with ATSC tuners have HD tuners.

“HD Monitor” is like an “HD Ready” TV; however if it’s called a monitor it is likely not to have any kind of tuner, analog or digital.

An “HD Ready” TV or “HD Monitor” can be connected to a digital cable box or satellite receiver, and does not need any additional boxes to work with these.

All of these issues are becoming moot since the FCC requires new sets to come with built-in tuners. If you buy a late model HDTV set, it will have a tuner. “HDTV ready” is going to disappear.