What is the use of manifest.json in React app?

Question

I deleted it while setting up a react project. After that project runs fine but it shows one error on the console (Line 1, syntax error)

Answer 1

It "provides information about an application such as name, author, icon or icons, description, and more." Definition found here

Another good explanation at MDN

Here is a good video explanation for building PWAs (something manifest is often used to facilitate)