The ::-moz-placeholderpseudo-element represents any form element displaying placeholder text. This allows web developers and theme designers to customize the appearance of placeholder text, which is a light grey color by default. This may not work well if you've changed the background color of your form fields to be a similar color, for example, so you can use this pseudo-element to change the placeholder text color.
In Mozilla applications like Firefox, the -moz-outline-radius CSS property can be used to give outlines rounded corners. An outline is a line that is drawn around elements, outside the border edge, to make the element stand out.