Hydrochloric acid is the aqueous solution of hydrogen chloride in water. It is a strong, highly corrosive mineral acid and the primary componant of gastric acid within the stomach.
Hydrochlorides are salts resulting from the reaction of hydrochloric acid with an organic base (usually an amine/alkaloid). Converting insoluble (freebase form) amines/alkaloids into hydrochlorides is a common method of making them water- and acid-soluble. Many pharmaceutical substances are prepared as hydrochlorides so that they are quickly released in the gastrointestinal (GI) tract. The body usually absorbs a hydrochloride within 15-30 minutes. Hydrochlorides also typically have a longer shelf life compared to their freebases.