Cells are the basic living unit of organization for all forms of life. All cells arise from pre-existing cells. Everything between the plasma membrane and the nucleus. Bacteria have a nucleiod region with no membrane around the nuclear material. There are no organelles.
Cellular functions take place in the cytoplasm.
Almost all have cell walls for rigidity and protection. These cells have organelles which compartmentalize operations. Keeps raw materials together. Many operations are incompatible. Some products need to be stockpiled and stored.