Different cell organelles perform the following functions:
Cell wall is present only in plant cells. It protects the cell from external world, provides rigidity and shape as well as support.
Cell Membrane (also called as plasma membrane) is the only outer cell covering in case of animal cells. Like Cell wall, it also performs the basic function of protection and covering of the inner parts. Besides, its selectively permeable nature allows transfer of essential substances across the other, neighboring cells.
ER or Endoplasmic Reticulum is of two types. The rough ER has a role to play in protein synthesis and transport (because of the presence of ribosomes on its surface) and Smooth ER mainly helps in lipid synthesis, besides others.
Golgi Bodies (also called as the Golgi Apparatus or Golgi Complex) stores molecules synthesized by the ER, modifies them and then transports them to specific destinations across the cell for various uses.
Lysosomes are cellular vessicles containing specific cellular enzymes that are involved in cellular digestion.
Mitochondria produce energy or ATP molecules required by the cell to carry all its activities. It is also called as the power house of the cell for the same reason.
Chloroplasts are a class of plastids that contain the green pigment called as chlorophyll. They help in photosynthesis and thus food production. They are absent in heterotrophs.
The Nucleus stores the genetic or hereditary information of the cell, the DNA, in the form of chromatin material. It acts like a control center of the cell.
Nonetheless, the cell organelles have a limitless variety of other interlinked and separate functions to perform, (some of these, I believe, are under experiments and therefore yet to be discovered) that would require individual study and concentration.