// Owned pointer – only one thing can ‘own’ this pointer at a time
    // This means that when the `Box` leaves its scope, it can be automatically deallocated safely.
    let mut mine: Box<i32> = Box::new(3);
    *mine = 5; // dereference
    // Here, `now_its_mine` takes ownership of `mine`. In other words, `mine` is moved.
    let mut now_its_mine = mine;
    *now_its_mine += 2;

    println!("{}", now_its_mine); // 7
    // println!("{}", mine); // this would not compile because `now_its_mine` now owns the pointer

    // Reference – an immutable pointer that refers to other data
    // When a reference is taken to a value, we say that the value has been ‘borrowed’.
    // While a value is borrowed immutably, it cannot be mutated or moved.
    // A borrow lasts until the end of the scope it was created in.
    let mut var = 4;
    var = 3;
    let ref_var: &i32 = &var;

    println!("{}", var); // Unlike `mine`, `var` can still be used
    println!("{}", *ref_var);
    // var = 5; // this would not compile because `var` is borrowed
    // *ref_var = 6; // this would not either, because `ref_var` is an immutable reference

    // Mutable reference
    // While a value is mutably borrowed, it cannot be accessed at all.
    let mut var2 = 4;
    let ref_var2: &mut i32 = &mut var2;
    *ref_var2 += 2;         // '*' is used to point to the mutably borrowed var2

    println!("{}", *ref_var2); // 6 , // var2 would not compile.
    // ref_var2 is of type &mut i32, so stores a reference to an i32, not the value.
    // var2 = 2; // this would not compile because `var2` is borrowed.