Numerical integration is a mathematical technique used to estimate the value of an integral when it is difficult or impossible to calculate analytically. It involves approximating the area under a curve represented by a function, often using methods like the Trapezoidal Rule or Simpson's Rule. These methods break the area into smaller, manageable sections to provide an approximate total. This approach is particularly useful in fields such as physics, engineering, and computer science, where complex functions arise. Numerical integration allows for practical solutions in real-world applications, enabling calculations that would otherwise require extensive analytical work.