Scalar quantities are quantities in which the magnitude is stated, but the direction is either not applicable or not specified.
Vector quantities are quantities in which both the magnitude and the direction must be stated.
It does not make sense to say that you’re applying a force of 10 N on a box without stating the direction. The force can be directed anywhere. Hence, you need to specify which direction the force is applied: 10 N in the horizontal direction on a box.
There will be more about how to differentiate speed, displacement, velocity and acceleration in the later chapter.