The circle equation is a mathematical representation of a circle in a coordinate plane. The standard form of the equation is (x - h)^2 + (y - k)^2 = r^2, where (h, k) is the center of the circle and r is the radius. This equation helps in identifying the position and size of the circle. In this equation, x and y represent the coordinates of any point on the circle. By substituting different values for x and y, one can determine whether a point lies inside, on, or outside the circle. Understanding the circle equation is essential in geometry and various applications in science and engineering.