The tutorial by Divyun Vaid of SourceFuse explains how to build a real-time collaborative spreadsheet using modern web technologies, specifically focusing on the transition of office suites from heavy desktop software to lightweight, browser-based applications. The guide details the setup and implementation of a collaborative spreadsheet using technologies such as PubNub for real-time APIs and Handsontable for the spreadsheet module. It covers essential features like showing online users, highlighting active cells, synchronizing changes across editing sessions, and maintaining an audit trail for updates. The tutorial emphasizes using PubNub's infrastructure to manage changes and user presence, while Parcel is employed for quick prototyping. It also introduces hooks to record and replay changes, ensuring that updates are propagated across all user sessions. The goal is to create a seamless collaborative experience where multiple users can interact with the spreadsheet in real-time from different locations and devices.