Integration is a fundamental concept in calculus that refers to the process of finding the integral of a function, which represents the accumulation of quantities, such as areas under curves or total values over intervals. It can be viewed as the reverse operation of differentiation. There are two main types of integration: definite integration, which computes a specific numerical value over a given interval, and indefinite integration, which results in a general function plus a constant. Integration is widely used in various fields, including physics, engineering, and economics, to solve problems involving rates of change and accumulation.