Fall is to drop or come down freely under the influence of gravity. This is demonstrated when you toss a ball towards the sky, it fall’s back to the earth because of the gravitational force of the earth itself. Another explanation of fall is when you intentionally jump from a higher location to a lower place. The act of going down is called falling. A fall involves the free-fall of detached individual pieces of any size. This means that when an object falls, it is not in anyway in contact with place where it comes from and when it reaches the ground, that’s the time the object will have a contact with the ground.
Slide means move over a surface while maintaining smooth continuous contact. It usually implies rapid easy movement without loss of contact with the surface. An example is the children playing with the slide in the park. When a child slides, she has a continuous contact with the “slide” until she reaches the bottom. A slide occurs when material remains fairly coherent and moves along a well-defined surface.
Flow is to move or run smoothly with unbroken continuity, as in the manner or characteristic of a fluid. This is can be further understood by considering the river as example wherein the water is flowing or running smoothly and continuously. A flow occurs when material moves down slope as a viscous fluid. Most flows are saturated with water and typically move as lobes or tongues.