It is a hexagon all of whose sides are of equal measure. Note
that it need not be a regular hexagon since the angles need not be
equal (in the same way that a rhombus has four equal sides but its
angles are not all the same).
If that third of a hexagon is based on adjacent corner points
and the center point, then the resulting shape would be a rhombus,
which is a parallelogram with equal length sides, which in turn is
a quadrilateral whose opposite side are parallel.