Complex sentence: Synthetic cannabinoids are a class of designer drugs that are chemically different from the cannabinoids found in cannabis but which also bind to cannabinoid receptors and are often sold in products with claims that they give the effects of cannabis.
Split into simpler sentences: Synthetic cannabinoids are a class of chemicals that are different from the cannabinoids found in cannabis but which also bind to cannabinoid receptors. They are often marketed as designer drugs or sold in products with claims that they give the effects of cannabis.