Like fractions, decimals represent parts of a whole. In fact, all finite decimals (decimals that have an ending or repeat themselves) can be written as fractions. You probably already convert many fractions to decimals in your head without even realizing it, like converting to 0.5 or to 0.25.
You've been using decimals for years. Every time you spend money, you deal with decimals: fifty cents is usually written as the decimal $0.50. Whenever you weigh produce at the grocery store, you'll most likely get a decimal: that bag of avocados is 0.23 lb. Times at a swim meet? Decimals, decimals, decimals!
Read on to see how these guys work.