Understanding State and Props in React

React is a popular JavaScript library commonly used for developing user interfaces. Within the realm of React, data is primarily managed through two mechanisms - 'state' and 'props'.

What is State?

In React, 'state' is an object that stores values which may change over time, and affects the behavior or render output of a component. It is often described as being 'local' or 'encapsulated' as it is only accessible within the component where it is declared.

State allows a React component to create, read, and update its own data. Hence, it usually involves components that need to maintain and mutate internal data, like forms, or interfaces that need to be responsive to user interactions.

For example, if you're creating a toggle button, the "on" and "off" switch states are typically handled through 'state'.

What are Props?

On the other hand, 'props', short for properties, allows data to be passed from parent to child components in a top-down (or unidirectional) flow. They are read-only and a child component cannot directly modify its props - every time the parent component is re-rendered, the child component's props will receive the updated data.

For instance, if you have a parent component rendering a list, and items of the list are separate child components, these items can be passed as 'props' to individual child components.

The Correlation of State and Props

It's worth noting that props can also be used to pass down functions or event handlers from the parent component to a child component. These functions, when executed in the child component, may cause changes in the state of the parent component, thereby indirectly affecting the props passed to the child component.

Moreover, React's philosophy promotes the use of 'state' as sparingly as possible - it encourages developers to create 'stateless components' which only receive data through props and return what gets rendered.

Understanding and applying these - 'state' and 'props' - appropriately could greatly contribute to developing efficient React applications. By defining where the 'state' should live and how it should be updated, and passing data down to child components through 'props', we could achieve a non-complicated and predictable flow of data, making the React application easier to debug and maintain.