title: What's the recommended way to use "question mark" icon?
body: <p>I develop a desktop application, and I'd like to add a "question mark" icon besides one of the textbox (that describes the meaning of that textbox).</p>
  
  <p>My question is what's the common way to use the question mark:
  Should I show the text when hovering on the question mark? e.g. using a tooltip?
  Should I show the text just after clicking on the question mark?</p>
  
  <p>Thank you!</p>