Full spectrum means all the cannabinoids found in the plant are used. This includes CBD, THC, CBG and other cannabinoids. CBD is the main component of all these products. Any THC found in the product makes up less than 0.3%. At this measurement the residual euphoria and distraction that sometimes come with THC is avoided.
Full Spectrum is special because of the Entourage Effect. This effect creates a more powerful impact and occurs when cannabinoids are used together. For this reason full spectrum products are the strongest.