Reactivity is a concept used in the development of modern interactive web applications. It shows that when you make changes in value, it is automatically reflected in the DOM. For example, when an app is reactive, it means that any change of values (the result of user input) will be automatically reflected in the Document Object Model (DOM). DOM is a logical tree structure representing the HTML page a user can see in the browser or any other place where values are changed depending on the user input.
