Every system has some forces acting on it.  But when there are multiple forces acting on an object, it is simpler to figure out the net force (or the total force) on the object rather than trying to deal with each force individually.

And really, it is quite simple.  We just have to draw the force (from where it is originating), the magnitude of the force, and its direction.

In the first fram, we see a picture of a rock climber.  He is hanging from a rope, some distance above the ground.  Let's start by drawing the system diagram.

We draw the outline of the man, and all the forces on the man.  The rope is pulling him up, from his harness.  Gravity pulls him to the earth, this force originates upon his centre of mass, or his belly button.  He also has his foot on the cliff, so we draw both the normal force (perpendicular to the surface), and the force of friction of the cliff on his shoe.  Which is what we can see in the second frame.  This is only the first step in simplifying things.

The next step is to draw a free-body diagram (FBD), which is a diagram free of bodies.  The man becomes a point, or a dot, and the forces all originate from that dot.

If we assume that the man is not moving in any direction, we can say he is in static equilibrium, and that means that all forces are balanced.

In other words, the force of gravity is balanced by both the tension in the rope, and the small bit of friction on his foot.  When we add those vertical forces together, we get 0 N or a completely balanced vertical force. So he is not moving up, or down.

He is not moving towards, or away from the cliff, so the force with which he is pushing away from the cliff, is balanced by the force of the ropes pulling him back in (notice that F_T and F_fr are not perfectly vertical)

Consult the following for a method to draw the FBD:
http://physics.wku.edu/phys201/Information/ProblemSolving/ForceDiagrams.html