Coordinates are a system used to determine the position of a point in space. In a two-dimensional plane, coordinates are typically expressed as a pair of numbers, such as x, y. The x value indicates the horizontal position, while the y value indicates the vertical position. This system helps in mapping locations on graphs or in real-world applications like navigation. In three-dimensional space, coordinates are represented as a triplet, such as x, y, z. Here, the z value adds depth, allowing for a more complete representation of an object's position. This system is essential in fields like geometry, cartography, and computer graphics.