cargo build

This it used to build the project.
Cargo.toml is Cargo's configuration format. src directory contains source code

//1. Create a project named hello_cargo. it creates cargo.toml, src directory
$ cargo new hello_cargo
$ cd hello_cargo; dir
    Cargo.toml      //file
    src             //dir
$ cd src; cat main.rs
fn main() {
    println!("Hello, world!");
}

//2. Build project. exe is placed in target/debug
# cargo build                                                   //opt-level = 0
    Finished dev [unoptimized + debuginfo] target(s) in 0.0s
$ cargo build --release                                         //opt-level = 3
    Finished release [optimized] target(s) in 0.0s
# dir
target/debug/hello_cargo