Cells exist in many forms, primarily categorized as plant and animal cells. Each type has specific structures that determine its function. The cell membrane, cytoplasm, nucleus, and organelles play crucial roles in maintaining cellular processes. While plant cells have additional features such as a cell wall and chloroplasts, animal cells have structures specialized for mobility and metabolic processes. Understanding cell structures and their functions is essential for grasping how living organisms grow, develop, and maintain homeostasis.