In older Rust, you had to explicitly write the 'static lifetime in any static or const that needed a lifetime:

#![allow(unused_variables)]
fn main() {
mod foo {
const NAME: &'static str = "Ferris";
}
mod bar {
static NAME: &'static str = "Ferris";
}
}

But 'static is the only possible lifetime there. So Rust now assumes the 'static lifetime, and you don't have to write it out:

#![allow(unused_variables)]
fn main() {
mod foo {
const NAME: &str = "Ferris";
}
mod bar {
static NAME: &str = "Ferris";
}
}

In some situations, this can remove a lot of boilerplate:

#![allow(unused_variables)]
fn main() {
mod foo {
// old
const NAMES: &'static [&'static str; 2] = &["Ferris", "Bors"];
}
mod bar {

// new
const NAMES: &[&str; 2] = &["Ferris", "Bors"];
}
}