Extract = capsaicin extracted from the capsicum, aka capsicum oleoresin, which is added to the sauce as opposed to the capsaicin being in the sauce naturally from the existence of peppers.
Not only can this wreak havoc on your insides, the chemicals used to extract are often harsh and cause a metallic and/or bitter taste.
If I am not mistaken, Dave's Insanity was the first sauce to use an extract.