vega-scenegraph provides a scene graph representation and manipulation utilities for Vega visualizations. It handles the hierarchical structure of visual elements, enabling efficient updates and rendering. Key features include data binding, declarative specification of graphical marks, and support for various rendering backends like Canvas and SVG. This package forms a core component in Vega's pipeline, managing the visual representation of data for interactive visualizations. It's essential for developers building custom Vega applications.