All cannabinoids are produced as their acid variants (CBD-A) inside the plant. I.E. the plant has CBD-A in it when it is growing and harvested, not CBD. CBD-A is converted to CBD when heat, light, or oxygen exposure occurs; heat being the fastest way to get this conversion. This can happen naturally in the plant and in storage, to a small extent, but it is very minimal and happens slowly. Heating CBD-A removes the carboxyl group (the A) from the CBD-A, turning it into its active form, CBD. This process is known as decarboxylation. That is why CBD flower must be smoked or heated before making products with it. CBD-A has some purported medicinal benefits of note, but it is far less studied than CBD.