OneNote is described as an online, cloud-based notebook service that is simple to use, robust, and can be used on desktop and mobile devices. The document discusses how a teacher used OneNote with 147 students across 9 modules and found it helped with collaborative teaching and learning, organizing notes and materials, sharing content, and assessing student work. Key benefits identified include being able to find information faster, see live student work, provide feedback, and view curated reading materials. A few issues are noted, such as it not working well with weak internet connections, and potential conflicts when syncing pages across devices.