Mutable Variables

Rust variables are immutalbe by default. That means you can't change them after they've been set. The mut keyword makes them mutable allowing them to be changed after they are created.

Here's an example of creating a default (immutable) variable:

let alfa = String::from("apple");

And this is how to create one using the mut keyword to make it mutable:

let mut alfa = String::from("apple");