Why does Flexbox behave in this way?

Ok so i am very intrigued by this, why does flexbox arrange by default this labels in a column instead of a row? How does Css process this style?

Flexbox Behavior

Can someone explain me pls? I am missing something and i dont know what it is, how for example can i arrange this in a row?

You applied the flex property on the label which you intended to be a flex item.

You should rather wrap your labels elements with a div or so and then apply the flex property on the div, like so:

<div>
   <label>Name</label>
<label>Email</label>
<label>Age<span class="clue">(optional)</span></label>
 </div>

Then it will behave as expected .