These bindings provide an interface very similar to the pyspark API, but connect to a proprietary server -- called fuse-server -- rather than Spark. Like Spark, the server does most of the "heavy lifting", and the client bindings simply orchestrate the work via remote calls (RPCs).
Unlike Spark, however, fuse-server is a single self-contained binary that can be downloaded and run with a single command. The server is written in Rust, and is much faster and more efficient than Spark, when run against small or moderate-sized datasets (<=5TB).