Only changes in props and state trigger React to re-render components and updates the DOM.

The biggest difference is that re-rendering of the component based on input in state is done entirely within the component, whereas you with using props can receive new data from outside the component and re-render.

PropsAllows you to pass data from a parent component to a child component

//Parent Component
const books = () => {
    return (
        <div>
        <Book title = "Data structures and algorithms with JAVA" />
        </div>
    );
}
//Child component
const book = (props) => {
    return ( 
        <div>
            <h1>{props.title}</h1>

        </div>
    )
}

Explanation: Now. ‘props’ is passed in to the child component and the functional component the passes the ‘props’ as an argument which in turn will be handled as an object. The property ‘title’ is accessible in the child component from the parent component.

State

Only class-based react components can define and use state. It’s although possible to pass state to a functional component but functional components can’t edit them directly.

class NewBook extends Component {
    state = {
        number: ''
    };
    render() {
        return ( 
            <div>{this.state.number}</div>
        );
    }
}

As you can see the NewBook component contains a defined state. This state is accessible through this.state.number and can be returned in the render() method.