Centre Pivot and Lateral Move systems are self-propelled irrigation systems, which apply water to pasture or crop, generally from above the canopy.
Centre Pivot systems are anchored at one end and rotate around a fixed central point. Lateral systems are not anchored and both ends of the machine move at a constant speed up and down a paddock.
Centre Pivot and Lateral Move systems require an energy source to move water from the source to the plant as well as energy to move the machine on farm.
This from: http://irrigazette.com/en/news/invest-centre-pivot-or-lateral-move-systems.