- Diigo is a social bookmarking and annotation tool that allows users to bookmark webpages, highlight and annotate content, organize bookmarks into tags and lists, and share bookmarks and annotations with others. - It has features for personal and collaborative research including the ability to create groups for team projects. Users can also find popular bookmarks on topics and connect with others. - The document provides information on setting up educator accounts through Diigo, which allows teachers to create student accounts and class groups within the Teacher Console for assigning and managing student work.