Implementing a tutorial/introduction for a web application

I am looking for a library or some information on how to build an introduction to a website. These days you often find websites that offer an introduction to the different functions that the website offers. Usually it is a tutorial that darkens the entire page except some parts in a step by step fashion. These parts then are labeled with an explanation and the other darkened part of the website is not accessible for the duration of the introduction.

It is really hard to find information on this because of the key words 'tutorial' or 'introduction' which will usually lead you to tutorials of the searched framework or programming language.

I am programming in React so I would like to know resources that would help me or many a library that I can use for something like that. Even key words or a common name for this would help me already.