BRL-CAD is a comprehensive solid modeling system that provides tools for creating, editing, analyzing, and rendering 3D geometric models. The architecture is modular with core libraries (librt for ray tracing, libged for geometry editing, libgcv for format conversion, libbu for utilities, libbn for numerics) and multiple frontends including the MGED/QGED graphical editors, command-line tools, and a distributed ray tracing system (ADRT). Key entry points include mged/qged (interactive editors), rt (ray tracer), gcv (geometry converter), and various command-line utilities for analysis and processing. Data flows involve creating/editing geometry in the editors, storing in the internal WDB database, performing analysis (mass properties, volume), rendering via ray tracing, and importing/exporting CAD formats like STEP and IGES. The system demonstrates strong modularity, plugin-based extensibility, and cross-platform support through abstraction layers.