React Router is a standard library for routing in React. It enables the navigation among views of various components in a React Application, allows changing the browser URL, and keeps the UI in sync with the URL.

The React Context API is a way for a React app to effectively produce global variables that can be passed around. This is the alternative to "prop drilling" or moving props from grandparent to child to parent, and so on. Context is also touted as an easier, lighter approach to state management using Redux.

Essentially, useRef is like a “box” that can hold a mutable value in its .current property. If we pass a ref object to React with ref=myRef React will set its .current property to the corresponding DOM node whenever that node changes. The useRef returns a mutable ref object. This object has a property called .current. The value is persisted in the refContainer.current property. These values are accessed from the current property of the returned object. The .current property could be initialised to the passed argument initialValue e.g. useRef(initialValue). The object can persist a value for a full lifetime of the component.