The cytoplasm (not to be confused with cytosol) is the protoplasm of a cell outside the cell nucleus. It is the jelly-like material plus the organelles outside the nucleus, and inside the cell membrane.
Many important functions of a cell take place in organelles, which are like bits of machinery for doing many jobs. The cytoplasm is highly structured: it is not liquidy, but more of a gelatinous substance, even though it is made out of 75–80% water.
The cytosol contains a complex mixture of cytoskeleton filaments, including the endoplasmic reticulum and the Golgi apparatus. It includes dissolved molecules, and water that fills much of the cell. Due to this network of fibres, membranes and the many dissolved macromolecules such as proteins, the cytosol does not act like a simple liquid. The main function of the cytoplasm is to hold the organelles in place.