some docs

src/lib.rs

@@ -9,7 +9,18 @@
 //! * The trait [`StuffingStrategy`]
 //! * The trait [`Backend`]
 //!
-//!
+//! [`StuffedPtr`] is the main type of this crate. You it's a type whose size depends on the
+//! choice of [`Backend`] (defaults to `usize`, `u64` and `u128` are also possible). It can store a
+//! pointer or some extra data, so you can imagine it being
+//! ```rust
+//! enum StuffedPtr<T, E> {
+//!     Ptr(*mut T),
+//!     Extra(E),
+//! }
+//! ```
+//! except that the extra data is bitstuffed into the pointer. You can chose any arbitrary bitstuffing
+//! depending on the [`StuffingStrategy`], an unsafe trait that governs how the extra data
+//! (or the pointer itself) will be packed into the backend.
 
 mod backend;
 mod strategy;