An integral is a fundamental concept in calculus that represents the accumulation of quantities. It can be thought of as the area under a curve on a graph. For example, if you have a function that describes how fast a car is moving over time, the integral of that function gives you the total distance traveled. There are two main types of integrals: definite and indefinite. A definite integral calculates the area under a curve between two specific points, while an indefinite integral represents a family of functions and includes a constant of integration. Both types are essential for solving various problems in mathematics and physics.