В чем разница между Some(v) и Some(&v)?

И code block 1, и code block 2 в приведенном ниже коде работают, но я не знаю, почему.
В чем разница между Some(&number) и Some(number) ?

use std::collections::HashMap;

fn call(number: &str) -> &str {
    match number {
        "798-1364" => "We're sorry, please hang up and try again.",
        "645-7689" => "Hello, what can I get for you today?",
        _ => "Hi! Who is this again?"
    }
}

fn main() { 
    let mut contacts = HashMap::new();

    contacts.insert("Daniel", "798-1364");

    //====== code block 1
    match contacts.get(&"Daniel") {
        Some(&number) => println!("Calling Daniel: {}", call(&number)),
        _ => println!("Don't have Daniel's number."),
    }

    //====== code block 2, without '&'
    match contacts.get("Daniel") {
        Some(number) => println!("Calling Daniel: {}", call(number)),
        _ => println!("Don't have Daniel's number."),
    }

}