Sigma notation is a mathematical shorthand used to represent the summation of a sequence of terms. It is written using the Greek letter Σ, followed by an expression defining the terms to be summed. The formula includes limits of summation, indicating where to start and stop. Common summation formulas include those for arithmetic and geometric series, powers of integers, and more. Sigma notation is widely applied in calculus, statistics, and computer science for simplifying expressions. For instance, it’s used to calculate total costs, probabilities, or areas under curves. Understanding these basics helps in solving real-world and theoretical problems efficiently.