If you taste a substance that is an acid, like lemon juice or vinegar, it tastes sour. Vinegar, orange juice and grapefruit are all common acids. Strong acids include nitric acid, hydrochloric acid, and sulfuric acid. You should never taste strong acids. It would be fatal.
Hydrochloric acid is a strong acid found in the stomach of humans.
Hydrochloric acid, HCl, is very strong, and helps to break down the food you eat so your body can use it. The HCl would burn your skin if you spilled it on yourself. But the stomach is lined with lots of mucus layers that protect the rest of your organs from the acid. Bases contain hydroxide ions. The more hydroxide ions, the stronger the base.