Legend

 Fnet = net force m = mass a = acceleration Fg = force of gravity FN = normal force
 The floor pushes up and to his left with a reaction force Fr.  It has components Ff (keeping him from sliding) and Fn (keeping him on the floor equal to his weight).

Weight

When studying the motion of earthly objects (vector kinematics), and the forces that make them change speed/direction (dynamics), there is always one force at work: the gravitational pull of earth (Fg).
 Fg = mg where g = acceleration caused by gravity's pull.  It equals approximately 9.81 m/s2 for objects near the earth.   We will later on derive the value of g in the gravitation section.
Any object has a mass that is universal in any part of the universe, although its weight depends on the local gravity.  For example, an apple has mass of 0.1 kg anywhere in the universe, but its weight on the surface of the Earth is approximately 1 N (0.1 kg X 9.8 m/s2 = 0.98 N).

Weight acts down, it behaves as an external force acting on an object.   In effect, the Earth pulls down on the object and the object pulls up on the Earth as an reaction force or normal force, FN.

 Example:
 The free-body diagram shows the two forces acting on the standing person.  The normal force is distributed over both feet.Normal force, FN is actually the force exerted perpendicularly on a supporting surface (such as floor, pillar, or roadway) supporting the weight.  The weight of a brick resting on a floor numerically equals the downward load on the floor, and the equal and opposite force on the brick exerted by the floor is the upward normal force.
 Vector Dynamics Friction