shouldComponentUpdate allows the developer to prevent unnecessary re-rendering of a component by returning false if a render is not required. componentDidMount is called once the component has 'mounted' (the component has been created in the user interface, often by associating it with a DOM node). This is commonly used to trigger data loading from a remote source via an API. render is the most important lifecycle method and the only required one in any component. It is usually called every time the component's data is updated, reflecting changes in the user interface.