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DTV stands for Digital Television, which simply defines that the broadcast signal is being transmitted in digital form (normally in either MPEG-2 or MPEG-1 format). The term itself doesn't define how the signal is being transmitted or which resolution it should use.
In "real life", Europe has chosen to use existing PAL resolution in digital broadcasting, but Americans and most notably Japanese, have opted to use the "subset" of DTV, called HDTV in their broadcasts which offers native 16:9 aspect ratio and higher video resolution.
In Europe, three transmission standards are being used, DVB-T, DVB-C and DVB-S.