What does it mean to have one plane of separation in electrophesis?

"Electrophoresis can be one dimensional (i.e. one plane of separation) or two dimensional. One dimensional electrophoresis is used for most routine protein and nucleic acid separations. Two dimensional separation of proteins is used for finger printing , and when properly constructed can be extremely accurate in resolving all of the proteins present within a cell (greater than 1,500). "What does it mean to have one plane of separation in electrophesis?Your elaboration answers your question. I am going to assume this question has to do with gel electorphoresis. When you perform electrophoresis in an agarose gel, the samples move in one direction along a flat gel. This is what is meant by one plane.