Why is displacement a vector quantity and not a scalar quantity?
A scalar quantity is one which can be described by its magnitude only and does not require a direction. Speed is a scalar quantity. A vector quantity, on the other hand, needs both magnitude and direction for its complete description. Velocity is a vector quantity.
Displacement is the difference between the initial position and the final position of a body. Displacement is a vector quantity and not a scalar quantity because it can be only described by using both magnitude as well as direction. Distance, on the other hand, is a scalar quantity, since we need to know only about the path taken. In comparison, the path does not matter in the case of displacement.
When describing the displacement of a body, we usually ask something like, "a body started from origin and reached the coordinates (4,5) in 10 seconds. Determine its displacement."
Hope this helps.