How to Display Tooltips on Mobile Forms
What interface element should you use to provide the user with helpful information about a form field?
If you were thinking a tooltip, you are correct. Tooltips are necessary for form fields that need more clarification than its field label can give.
For example, when the field label has an obscure term the user isn’t familiar with. Or, when you’re asking for information that’s more personal than normal and need to explain why it’s needed.