Generally most concentrates on the market here are very concentrated mixtures of very pure THC and occasionally CBD produced by solvent extraction or with supercritical CO2 and refined further by e.g. decarboxylation (by e.g. heating the extract in a vacuum oven), "winterization" (removal of waxes and other inactives by precipitating impurities from ultra cold 95% ethanol), high temperature vacuum stripping/"distillation", etc.
Presumably they are much more psychoactive and potent than simple ethanol extract of cannabis.