What is the difference between await and block_on

The await keyword suspends execution of an async function until a Future completes, while block_on runs an async block to completion on the current thread, blocking it until the result is ready. Use await inside async functions to pause and resume tasks, and use block_on in synchronous entry points like main to start the async runtime.

use std::time::Duration;

fn main() {
    trpl::block_on(async {
        println!("Starting async task");
        trpl::sleep(Duration::from_millis(500)).await;
        println!("Task complete");
    });
}

Think of await as a polite pause button that lets other work happen while you wait for a result, whereas block_on is the engine that starts the whole process and waits for it to finish before letting the program exit. You use await inside your async code to handle delays, and you use block_on once at the very start of your program to kick everything off.