SSB = Single Side Band. A normal AM transmission has a spectrum diagram that has a carrier (at the freq you tune to) and 2 side identical sidebands mirrored about the carrier frequency. The carrier serves no useful purpose, and each sideband carries a complete encoding of the audio modulation, so 2 are redundant...Normal AM has the advantage of requiring minimally complex demodulation circuitry, but wastes roughly half it's power (and RF spectrum space) putting out a redundant sideband, and some useless carrier energy. In ham radio and several other applications wasting energy and spectrum is not worth a keeping a simple demodulator circuit in the receiver so they transmit in SSB to reduce wasted power....There is one further advantage to SSB a linear RF amp (used as a ham TX booster) has a average MAX power limit with respect to the spectrum you put in so if you put in half the spectrum you can push twice the effective TX power through your rig and get twice the distance.
SSB is used almost exclusively for Ham/Amateur radio, with the exception of one of the government news/entertainment channels on SW (VOA IIRC).
I'll admit I never took the time to study all the subtleties of SSB circuits so I can't explain their operation well, but when you hear a SSB station with an AM reciever it will will sound like a series of oddly pitched chirps/bass groans with a cadence matching muffled human speech. If your receiver has SSB and you switch to it you will have to adjust a BFO (beat frequency oscillator, sometimes labeled SSB sync), and sometimes tuning till those tones become intelligible speech.
There is also Synchronous Selectable Sideband which might be INCORRECTLY abbreviated SSB. Synchronous AM detection and Single Side Band are two totally different creatures with different uses and should not be confused with eachother.
My Sony has both SSB and a synchronous detector. The synchronous detector is for NORMAL AM and NOT SSB....The synchronous detector is supposed to help with noise and fading on normal AM, but it usually goes unused on my set since I have not found much benefit from it in practice.
Unless you plan to listen to hams (I like to spy on hams
) or VOA SSB is not useful. Synchronous detectors might be useful, but I've never needed them.