A billion is a numerical value represented by the digit 1 followed by nine zeros, or 1,000,000,000. It is a significant milestone in counting and is often used to describe large quantities, such as population figures or financial amounts. For example, the population of the world is estimated to be over 7 billion people. In the context of time, a billion seconds is approximately 31.7 years. This perspective helps illustrate just how large a billion is compared to smaller units, such as thousands or millions. Understanding billions is essential in fields like economics, science, and technology, where large numbers frequently occur.