An assembly of vesicles and folded membranes within the cytoplasm of eukaryotic cells that forms part of the endomembrane system. It modifies proteins and packages them and other materials (e.g. polysaccharides) for delivery to the plasma membrane for secretion or to destinations within the cell. Proteins arrive in vesicles following their assembly in the endoplasmic reticulum (ER), are processed within a membranous compartment, or cisterna, and ultimately sorted into Golgi vesicles for secretion, storage, or transport to lysosomes. As it ‘matures’ each cisterna gradually moves through the stack. The region of the stack nearest to the ER is called the cis Golgi, the middle zone is the medial Golgi, and the area where Golgi vesicles are released is the trans Golgi. Plant cells usually contain smaller arrays of Golgi-type vesicles, called dictyosomes. Some macromolecules are manufactured in the Golgi, such as certain noncellulose polysaccharides in plant cells. The apparatus is named after its discoverer, Camillo Golgi.

http://micro.magnet.fsu.edu/cells/golgi/golgiapparatus.html A succinct account of the Golgi apparatus from a site hosted by Florida State University