Everything I've written.

What a syscall is and why the kernel sits between your program and the hardware. Also why I/O does not mean slow, and why the real waiting happens inside the accept loop rather than in code you write.

Why "cannot infer type parameter" happens when a generic is built but never used, how to resolve it, and how to read what a generic function actually demands.

Why `.route(...).route(...)` chains work. A method taking `self` by value consumes the receiver and hands it back, and the three receiver forms decide what move semantics protect you from.

Why Rust has no exceptions. `Result<T, E>` makes failure an ordinary value the caller must handle, and four tools (`match`, `?`, `unwrap`, `expect`) answer it.

Why calling an `async fn` in Rust runs no code, and how the compiler turns the function body into a resumable state machine whose await points become enum states.