Full AM signal vs DSB-SC
With simple (less than 100%) modulation (as used in broadcast music channels) you get this: -



If you go over 100% modulation, the troughs in the modulated waveform above start to become small peaks with a reversal of phase of the carrier: -



In this scheme, because the carrier reverses phase each half cycle of the modulator there is, in effect, no carrier frequency amplitude and hence it is called "suppressed carrier".

Here is a picture of three DSB waveforms with different levels of modulation: -



Hopefully you should be able to see in the bottom picture the anomaly in the carrier as modulation rises past 100%. This prevents it from being used for transmission to radios that have a simple diode envelope detector.