An imaginary line that connects points of equal height value eg the elevation of the land surface above or below a vertical datum, in this case of LINZ topographic mapping, this is Mean Sea Level.

Data Dictionary for contour: http://apps.linz.govt.nz/topo-data-dictionary/index.aspx?page=class-contour

This layer is a component of the Topo250 map series. The Topo250 map series provides topographic mapping for the New Zealand mainland and Chatham Islands, at 1:250,000 scale.

Further information on Topo250: http://www.linz.govt.nz/topography/topo-maps/topo250