The document discusses React and D3. It defines React as a JavaScript library for building user interfaces that can update based on changing data. It is used by many large companies. D3 is a library for creating interactive data visualizations. Using React and D3 together allows creating reusable chart components with D3's math and data handling and React's rendering abilities. However, integrating the two requires care due to differences in how each treats data. Code examples and links are provided.