The sauce is a cannabis extract so called because of its liquid and sticky consistency. Known for its high levels of terpenes, the sauce is primarily enjoyed for its robust flavor profiles along with its potent potency. It is generally produced through a unique process that is designed to create a two-part final product comprised of cannabinoid-rich crystals with high levels of THC suspended in terpene-rich oil. This oil is the sauce and it's great if you're looking for a tasty pre-roll experience.
Diamonds are the crystals that form in the sauce. While sauce is normally added for flavor, since diamonds are essentially tasteless, otherwise it has recently been introduced into pre-rolls. Diamonds contain THCA, which isn't intoxicating on its own, but turns into intoxicating THC once heated to the right temperature. Because of the high purity and the labor involved in extracting them, diamonds tend to be more expensive and are highly revered for their potency.
Anyone interested in flavor should look for precooked products that contain an infusion of terpenes derived from cannabis. This natural source allows for a much better taste experience.