* AM (amplitude modulation) is the oldest and most common mode of radio communication. In AM, the amplitude of the carrier wave is varied in accordance with the audio signal. AM is susceptible to noise and interference, but it is also relatively simple to implement and has good range.
* FM (frequency modulation) is a more modern mode of radio communication that is less susceptible to noise and interference than AM. In FM, the frequency of the carrier wave is varied in accordance with the audio signal. FM is typically used for high-quality audio transmissions, such as music and voice.
* LSB (lower sideband) and USB (upper sideband) are two single-sideband (SSB) modes of radio communication. In SSB, only one sideband of the carrier wave is transmitted, which reduces the bandwidth required for transmission. SSB is more efficient than AM and FM, and it is also less susceptible to noise and interference. LSB and USB are typically used for voice communications.
The choice of mode depends on the specific application. For long-distance communication, SSB is typically used. For local communication, AM or FM may be used.