We start with all of the cells in digital logic state "0." Then watch closely as we send in "1"’s to first A, then B, then C.

As the charge in each cell is rearranged, electrostatic repulsion causes the charges in the neighboring cells to adopt the same arrangement. But if adjacent cells disagree, a cell will adopt the same setting as the majority of its neighbors.

Thus the output cell only changes to a logic state "1" after both the A and B inputs change to "1" (making the majority of the three inputs "1"). The setting of input C then makes no difference.