Whiteboard is a lightweight, NodeJS-based collaborative sketchboard that can be easily customized to your needs. It allows multiple users to draw and write together in real-time, with each user's cursor visible to others. The app provides a range of features including the ability to undo and redo actions, drag and drop or copy and paste images or PDFs, resize, move, rotate and draw images, write text and sticky notes, and save the whiteboard to an image or JSON. You can also draw angle lines and squares by pressing 'Shift' while drawing. The app is compatible with PC, tablet, and mobile devices, and can be used in various projects such as WebRTC conference tools and online collaboration learning activities.