React code is made of entities called [[Component-based software engineering|components]].{{sfn|Wieruch|2020}}{{rp|10-12}} These components are modular and reusablecan be reused.{{sfn|Wieruch|2020}}{{rp|70}} React applications typically consist of many layers of components. The components are rendered to a root element in the [[Document Object Model|DOM]] using the React DOM library. When rendering a component, values are passed between components through ''props'' (short for "properties")''.'' Values internal to a component are called its ''state.''<ref>{{cite web |title=Components and Props |url=https://reactjs.org/docs/components-and-props.html#props-are-read-only |url-status=live |access-date=7 April 2018 |website=React |publisher=Facebook |archive-date=7 April 2018 |archive-url=https://web.archive.org/web/20180407120115/https://reactjs.org/docs/components-and-props.html}}</ref>
The two primary ways of declaring components in React are through function components and class components.{{sfn|Wieruch|2020}}{{rp|118}}{{sfn|Larsen|2021}}{{rp|10}}
