Ribosomes, along with RNA (m, t, and r), work to produce proteins. If ribosomes are located on the endoplasmic reticulum, then it is called a rough endoplasmic reticulum (due to the "bumpy" appearance given by the ribosomes).
The endoplasmic reticulum takes the proteins that are made by the ribosomes and folds them into sacs that are called cisternae. It then transports these folded proteins to the Golgi apparatus.
The Golgi apparatus is a series of membranes that look like flattened pancakes. Molecules leave the ER in what are called transition vesicles (sacs) and enter the Golgi apparatus. When the molecules enter the Golgi apparatus they are stored and charged. They are then released from the Golgi apparatus in what are called secretory vesicles into the cytoplasm. From there, the materials are delivered to the cell membrane and exit the cell.