Rust: What is the difference between chain and zip?

1let a = vec![1, 2, 3];
2let b = vec![4, 5, 6];
3
4// Chain: [1,2,3,4,5,6]
5let chained: Vec<&i32> = a.iter().chain(b.iter()).collect();
6
7// Zip: [(1,4), (2,5), (3,6)]
8let zipped: Vec<(&i32, &i32)> = a.iter().zip(b.iter()).collect();