# Modules

We have seen how `impl` blocks let us namespace functions to a type.

Similarly, `mod` lets us namespace types and functions:

```rust,editable
mod foo {
    pub fn do_something() {
        println!("In the foo module");
    }
}

mod bar {
    pub fn do_something() {
        println!("In the bar module");
    }
}

fn main() {
    foo::do_something();
    bar::do_something();
}
```

<details>

* Packages provide functionality and include a `Cargo.toml` file that describes how to build a bundle of 1+ crates.
* Crates are a tree of modules, where a binary crate creates an executable and a library crate compiles to a library.
* Modules define organization, scope, and are the focus of this section.

</details>