PyGEOS is a C/Python library with vectorized geometry functions. The geometry operations are done in the open-source geometry library GEOS. PyGEOS wraps these operations in NumPy ufuncs providing a performance improvement when operating on arrays of geometries.
Important note : PyGEOS was merged with Shapely ( https://shapely.readthedocs.io ) in December 2021 and will be released as part of Shapely 2.0. The development will take place at the Shapely repository. Please raise issues or create pull request over there. PyGEOS itself will receive updates (by backporting from the Shapely repository) until Shapely 2.0 is actually released.
A universal function (or ufunc for short) is a function that operates on n-dimensional arrays in an element-by-element fashion, supporting array broadcasting. The for-loops that are involved are fully implemented in C diminishing the overhead of the Python interpreter.