An acid is a substance that releases hydrogen ions into an aqueous solution. A base is a substance that releases hydroxide ions.
Acids are sour, gives burning sensation, generally sticky, reacts with metals to produce hydrogen gas. Although bases are opposite as they are bitter, generally odorless (except ammonia), they are slippery; bases react with fats and oils. In phenolphthalein, indicator acids remain colorless, and base gives pink color.