The nucleus is the place where DNA is located and is where RNA is transcribed. The nucleolus is usually visible as a dark spot in the nucleus and is the site of ribosome formation. They are quite small, made up of 50 proteins and several long RNAs intricately bound together. They have no membrane and disassemble into two subunits when not actively synthesizing proteins. Mitochondria are the sites of aerobic respiration and generally are the major energy production center in eukaryotes.
Chloroplasts are the site of photosynthesis in plants only.
They have a double membrane. The Endoplasmic Reticulum is the transport network for molecules targeted for modification and specific final destinations. The Golgi Apparatus modifies molecules and packages them into small membrane bound sacs called vesicles. They digest waste materials and foods within the cell, breaking down molecules into their base components using strong digestive enzymes. This was intended as a very brief review, click details for more information.