expression

function

Anything that returns a value.

e.g.
5
bool values
add(3,4)
if condition {value1} else {value2}
({code}) - code block

    let _x = {
        let price = 5;
        let qty = 10;
        price * qty
    };
    println!("Result is: {}", _x);
    let y = add(4,6);
    println!("Value of y is : {}", y);
    println!("Value from function 'add' is {}.", add(3,1));