Rust: What is the difference between Arc<Mutex<T>> and Arc<AtomicX>?

1use std::sync::{Arc, Mutex};
2use std::sync::atomic::{AtomicU64, Ordering};
3
4// Counter with Mutex
5let counter = Arc::new(Mutex::new(0u64));
6let counter_clone = Arc::clone(&counter);
7std::thread::spawn(move || {
8    *counter_clone.lock().unwrap() += 1;
9});
10
11// Counter with AtomicU64
12let counter = Arc::new(AtomicU64::new(0));
13let counter_clone = Arc::clone(&counter);
14std::thread::spawn(move || {
15    counter_clone.fetch_add(1, Ordering::SeqCst);
16});