Rahul Kumar's presentation at LinuxCon 2015 covers the creation of reactive dashboards using Apache Spark, detailing key features like real-time data updates and interactivity. It provides an overview of Spark's capabilities, RDDs (Resilient Distributed Datasets), and Spark SQL for structured data, along with practical examples and setup instructions. The session emphasizes building responsive and resilient applications through reactive programming with tools like Play Framework and Akka.