In-context descriptions or hints can help clarify what goes inside each form field, and therefore improve completion and conversion rates. There are many ways to provide hints. A common implementation is by inserting instructions within form fields. Unfortunately, user testing continually shows that placeholders in form fields often hurt usability more than help it.
Labels and Placeholders
Labels tell users what information belongs in a given form field and are usually positioned outside the form field. Placeholder text, located inside a form field, is an additional hint, description, or example of the information required for a particular field. These hints typically disappear when the user types in the field.