D3 is a powerful JavaScript library used for creating dynamic and interactive data visualizations in web browsers. It allows developers to bind data to Document Object Model (DOM) elements and apply data-driven transformations to the document. This makes it easier to create complex visual representations of data, such as charts, graphs, and maps. One of the key features of D3 is its ability to work with various data formats, including JSON and CSV. It also supports transitions and animations, enhancing the user experience. By leveraging SVG (Scalable Vector Graphics) and HTML5, D3 enables the creation of visually appealing and informative graphics that can be easily integrated into web applications.