To create a new variable binding in Rust, we use the following form:

let x = 1; 

This means that we create a new variable binding called x whose content will be 1. The default type for numbers depends on the situation a bit, but usually it's a 32-bit signed integer. If we need a variable that can change, we use this form:

let mut x = 1; 

By default, all variables in Rust are non-mutable; therefore, we have to explicitly define a variable as being mutable.