Rust: What is the difference between async fn and fn returning Future?

1// async fn
2async fn get_data() -> String {
3    String::from("data")
4}
5
6// fn returning Future
7use std::future::Future;
8use std::pin::Pin;
9
10fn get_data() -> Pin<Box<dyn Future<Output = String> + Send>> {
11    Box::pin(async {
12        String::from("data")
13    })
14}