Why DVB-T (Digital Video Broadcasting - Terrestrial) is the digital ATV standard borrowed from European broadcast TV. It uses COFDM, thousands of closely spaced subcarriers, and each subcarrier is modulated with a phase/amplitude scheme: QPSK, 16-QAM or 64-QAM depending on the robustness and data rate you want. So the modulation on the individual carriers is quadrature phase shift keying or quadrature amplitude modulation.
Watch out The FM choice describes analog fast-scan ATV on the higher microwave bands or FM broadcast audio, not DVB-T; AM with vestigial sideband is the old analog NTSC-style ATV video scheme, and on-off keying is basically CW.
DVB-T = digital = COFDM carriers keyed with QPSK/QAM. Digital standard, digital modulation.