Acids and bases are similar in that they both release ions into water, change the color of litmus paper, combine with one another to form salts and water, and corrode materials and burn human tissue when used in sufficient strength. They differ in which ions they release in water.
Acids release hydrogen ions into water; bases release hydroxide ions into water. Their differing chemical properties are based on this: acids corrode metals when the hydrogen bonds with metal, while the hydroxide ions in bases destroy proteins.
Another difference between acids and bases is their taste. Acids taste sour, while bases taste bitter. Because it is not safe to taste chemicals in a laboratory setting, this is not a recommended test to differentiate between acids and bases. Tasting bases is particularly hazardous due to their ability to destroy proteins in the human body.
The relative strength of acids and bases is determined by the number of ions in solution, not by how concentrated they are. Differences in acid and base concentration are referred to as dilute or concentrated, not strong or weak. Common strong acids are sulfuric acid, nitric acid and hydrochloric acid; common strong bases are sodium hydroxide and potassium hydroxide. Strong acids and bases corrode materials more quickly due to the larger number of ions available for the reaction.