Within elements the airfoils of the wing are defined. Each section can have one or more elements. Within each element one airfoil have to be defined. If e.g. the wing should have a step at this section, two elements can be defined for the two airfoils.

Mathematically spoken a element is a coordinate system that is translated, rotated and scaled relative to the section coordinate system. This transformation parameters are defined withing the transformation section. The wirfoil, which is linked by using the parameter airfoilUID is directly 'copied' in the element coordinate system. If e.g. the airfoil is defined from 0 to 1 in x-direction and the total scaling of the elements x-axis equals 3.5 the wing chord is 3.5 m long.

An example for wing element can be found in the picture below:

Reference