Rust: What is the difference between tokio::spawn and rayon::spawn?

tokio::spawn — async task. rayon::spawn — CPU thread.

tokio::spawn:

• Async.
• I/O-bound.
• Non-blocking.

rayon::spawn:

• CPU-bound.
• Blocking.
• Parallel.

1// tokio
2tokio::spawn(async {
3    let data = fetch().await;
4    process(data);
5});
6
7// rayon
8rayon::spawn(|| {
9    heavy_computation();
10});

Key: tokio for async, rayon for parallel CPU.