📝[no ci] Updated README

README.md

@@ -23,3 +23,32 @@ pytest
 ```bash
 cargo bench -F criterion -p cfpyo3_rs_core -- --verbose
 ```
+
+## Architecture
+
+This project is divided into four parts - looks clumsy, but I'll introduce them and explain their necessity.
+
+### `cfpyo3_rs_core`
+
+This is the Rust core of the project, and is meant to be responsible for the heavy lifting. Its necessity is almost self-explanatory.
+
+### `cfpyo3_rs_bindings`
+
+This one looks redundant at first glance, as we already have `cfpyo3_rs_py`. Initially this member did not exist, until I find some bindings in `cfpyo3_rs_py` very useful, want to reuse them, and failed because:
+
+- It is not an `rlib`.
+- Even I managed to make it an `rlib`, it's just not good to import the whole package because `cfpyo3_rs_py` itself is exposing lots of APIs to Python.
+
+Another choice is to put these useful bindings in `cfpyo3_rs_core`, but then GitHub CI cannot build it for whatever reason.
+
+So at last, this member is born.
+
+### `cfpyo3_rs_py`
+
+This is the 'direct' Python bindings of this project. It is just a REALLY thin wrapper around `cfpyo3_rs_core` and `cfpyo3_rs_bindings`, and is responsible for exposing the APIs to Python.
+
+### `cfpyo3`
+
+This is the Python package that users will interact with. It is a relatively thin wrapper that dispatches the calls to `cfpyo3_rs_py`.
+
+> A typical use case is the `f32` & `f64` dispatch.