Is the representation of the pointing vector, where ab represents the starting point of the vector and bc represents the ending point of the vector. Vector is a quantity composed of direction and magnitude, which can be used to represent the displacement and velocity of an object. A vector is usually represented by an arrow, the starting point of which represents the starting point of the vector, and the ending point of which represents the ending point of the vector. Mathematically, a vector can be expressed as an ordered number pair, where ab and bc represent the components of the vector on the X axis and Y axis respectively. For example, a vector indicates that the component on the X axis is 3 and the component on the Y axis is 2.