function in Rust

A function definition specifies what and how a specific task would be done. 
A function must be called so as to execute it. This process is termed as function invocation.
Functions may also return a value along with control, back to the caller. 
Parameters are a mechanism to pass values to functions. Parameters form a part of the function’s signature. 
/*
fn main() {
    println!("Hello, world!");
    another_function();
}

fn another_function() {
    println!("Another function.");
}
*/