HTTrack is an offline browser utility that allows users to download an entire website from a server to a local directory by crawling it. This process, known as website mirroring, creates an archive or replica of the site that can be analyzed locally. The document provides step-by-step instructions for downloading and installing HTTrack, inputting the target website URL, scanning and saving files, and reviewing the mirrored website saved on the local machine. It notes that mirroring a site allows for thorough footprinting and analysis of the target organization's website content offline.