AM, or amplitude modulation, was once the dominant voice mode. Today it has largely been replaced by SSB, for its better weak-signal performance, and FM on VHF/UHF repeaters, for its better suppression of noise.
However, AM continues to attract interest, and has even undergone something of a revival. In Australia there are regular AM nets on 160 and 80 metres. AM is also heard on 40 metres from time to time. AM devotees appreciate the mode's (alleged) superior voice quality compared to SSB. They also find that AM offers the opportunity to use vintage equipment - often homebrewed or modified ex-commercial equipment. Listeners are particularly attracted to 160 metres AM - the mode can be monitored simply by retuning many AM broadcast radios to cover up to 1.8 MHz. For this reason, WIA Divisions and clubs in some states still use 160m AM as one frequency for their weekly broadcasts.