What is the difference between iter and into_iter

Use iter() to borrow elements without moving them, and into_iter() to take ownership and move elements out of the collection.

let numbers = vec![1, 2, 3];

// Borrow: numbers is still usable after the loop
for n in numbers.iter() {
    println!("{n}");
}

// Move: numbers is consumed and cannot be used after the loop
for n in numbers.into_iter() {
    println!("{n}");
}

Use iter() when you just need to read the data and keep the original list for later use. Use into_iter() when you want to consume the list entirely, like moving items from a box to a new location where the original box is now empty.