QAM can be used in many radio communications and data delivery applications. However some specific variants of QAM are used in some specific applications and standards.
For domestic broadcast applications i.e. 64 QAM and 256 QAM are often used in digital cable television and cable modem applications. In the UK, 16 QAM and 64 QAM are currently used for digital terrestrial television using DVB - Digital Video Broadcasting. In the US, 64 QAM and 256 QAM are the mandated modulation schemes for digital cable as standardized by the SCTE in the standard ANSI/SCTE 07 2000.
In addition to this, variants of QAM are used in GSM/WCDMA/LTE technologies. But I am not clear what you are looking into but following image can clarify a bit -
