Rust: What is the difference between Future and Stream?

Future — single value. Stream — sequence of values.

Future:

• Resolves to one value.
• Poll once.
• For async operations.

Stream:

• Produces multiple values.
• Poll repeatedly.
• For async iteration.

1use futures::stream::{self, StreamExt};
2
3let mut stream = stream::iter(vec![1, 2, 3]);
4while let Some(val) = stream.next().await {
5    println!("{}", val);
6}

Key: Future for single async result, Stream for multiple.