What is the Normal Force (FN)?

The normal force is not...
• ...a force that's just like the other forces.
• ...an ordinary force.
• ...an action-reaction force pair of an object's weight

The common meanings of the word "normal" do not apply.  In the case of the Normal Force what is actually being described is geometry.

 If two lines are at right angles to each other, we call them perpendicular. If two surfaces are at right angles to each other, we call them orthogonal. If a surface and a line are at right angles to each other, we say the line is normal.  So any line that is at a right angle to the surface is called a normal line.If there is a force coming from the surface and at a right angle to the surface then we call it a Normal line. Any force coming from the surface and acting at a right angle to the surface is called the Normal Force.

 When an object is sitting on a level surface then the normal force is always equal and opposite of the weight of the object. On an inclined surface notice that... The angle of the incline and the angle of the weight away from the normal is the same size.. The weight continues to act straight down toward the center of the earth. The normal force is equal and opposite to the perpendicular force.