The camber determines the curvature of an aerofoil. The
thickness is measured from the top surface to the bottom surface at the point
of maximum thickness.
The relative thickness is the “thickness/chord ratio” (t/c ratio) and is the
maximum thickness of the aerofoil expressed as a percentage of the chord.
If you have a wing of say 8% t/c ratio and it has a chord of say 10 feet then
the point of maximum thickness will be 9.6 inches. (8 x 120 / 100 = 9.6)