Partio is a C++ library and toolkit for particle input/output and manipulation, primarily used in visual effects and simulation pipelines. It provides an abstraction layer for particle data (position, velocity, ID, etc.) with support for multiple file formats (BGEO, GEO, PDC, PDB, etc.) through a plugin-based I/O system. The repository includes core library code, command-line tools (partconvert, partinfo, partview), a Qt-based GUI editor (partedit.py), Python bindings via SWIG, and test suites. The architecture separates core data structures, format-specific handlers, and utilities like caching and KD-trees, enabling both direct library use and standalone tools for data inspection and conversion.