The demonstration we do in our show to help you learn about acids and bases uses a red cabbage to provide an indicator. An idicator is a chemical that changes color, depending on whether the solution that is poured into it is an acid or a base. For the purple water that is left behind when you boil red cabbage, a neutral solution will result in a blue-biolet color. An acid will be more read and a base will be more green. You can do a LOT of experiments with chemicals from your kitchen, pouring them into cabbage juice to find out if they are acids or bases.
Chemists measure acidity using pH. An acid has a low value of pH and a base has a higher value.
Every change of one unit in pH means a change of 10 times in the acid or base character of the chemical. The following are links to other pages with information about acids and bases College level page - that describes a LOT of things about acids and bases.