When labels are used, they often show up above the input field by default:
Email Label
By using floating labels, you can place the label inside the input field and have it move or animation when the input field is clicked:
Example
Notes on floating labels: The placeholderproperty is necessary for every <input> element (even if it is not displayed), and the <label> elements have to appear after the <input> element.
Textarea
This also applies to textareas:
Example
Select Menus
Additionally, “floating-labels” are an option for some menus. They won’t, however, levitate or become animated. The label will always show up inside the pick menu, in the upper left corner: