Evernote is a note-taking app that allows users to save notes, articles, and files in an organized manner across all devices. The document provides step-by-step instructions on how to sign up for an Evernote account, create notes and notebooks, add attachments, set reminders, sync devices, search notes, and use other key features like web clipping and shortcuts. Users are guided through the basics of getting started with Evernote to help them remember everything in an easy and organized way.