Buttons can do an action, display a menu, or both:
tooltip on button tooltip on button
Buttons have showLabel=false so text is not displayed. If no title attribute supplied, Should have label as title attribute displayed on mouse over
The button CSS as well as the icon CSS can change on toggle
Short button, tall buttons, big buttons, small buttons... These buttons size to their content (just like <button>).
Dojo users can customize styles. Here's an example:
clicking the buttons below will change the buttons above