String vs &str in Rust

Use String when you need to own and modify text, and &str when you only need to read a borrowed slice of text. String lives on the heap and is mutable, while &str is a reference to a string literal or part of a String that lives on the stack or elsewhere.

fn main() {
    let owned = String::from("hello");
    let borrowed: &str = "world";
    println!("{owned}, {borrowed}");
}

Think of String as a text document you own and can edit, while &str is just a view of someone else's text that you can read but not change. You use String when your program needs to create or modify text, and &str when you just need to pass text around without taking ownership.