Shareist is a content marketing tool that allows users to capture ideas and bookmarks, create projects with images and text, and share content instantly on social media. The document provides step-by-step instructions on how to sign up for a Shareist account, create projects, add images and text, connect social media accounts, and share or publish content to platforms like Facebook. Key features highlighted include capturing online content from RSS feeds or image searches, editing elements, and creating reports on social media performance.