No matter what tech stack you are using, upon builds of any kind, almost always you will see MANIFEST files. Manifest file is basically the one that contains the metadata for the project. Think about things like version number, licences, etc.

Interestingly, this term comes from "Ship Manifest", which is a document used in the shipping cargo industry. This document lists out the details of the ship, like its crew and cargo. Manifest files can have it's own format. Sometimes they are .txt files like cache-manifest in HTML5 or sometimes they are .json, like in webmanifest files. Manifest files are really important in package management as well.