`componentDidMount` is a lifecycle method in React class components. React automatically calls it right after the component has mounted and rendered for the first time. Overriding this method lets you run code that needs to happen once the component exists in the DOM.

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React executes the class constructor to initialize the states. After that, React mounts and renders the component for the first time. React provides us with a function that we can override to be executed at that time, called **componentDidMount**.

States can then be updated, and after re-rendering, we can execute code by overriding the **componentDidUpdate** function.

Finally, when a component is unmounted, we need to remove any unnecessary things from memory, such as timeouts. To do that, React exposes the **componentWillUnmount** function.

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