The electronic structure of an element is 2,8,6. What does this mean?

This mean the ground state (the lowest energy state) of the electronic structure of the element is :
In the first electronic shell (closest to the atomic nucleus), there are 2 electrons.
In the second electronic shell, there are 8 electrons.
In the third electronic shell (the outermost shell), there are 6 electrons.
There is no electron in the electronic shells outer than the third electronic shell.

Sum up the number of electrons. In an atom of the element, there are 16 electrons, and thus 16 protons. The element is sulfur and has an atomic number of 16.