FORMAT gives you a text representation of a binary value and even gives you some level of control as to how that textual representation looks like.
FIELDCAPTION gives you the Caption of a field in the user's chosen UI language. This is exactly the same string that is used as a label to a control on a form that uses the field as a SourceExpression unless you changed the label's or Textbox's Caption, CaptionML or Name property. Note that this function adds MultiLanguage functionality and ensures a consistent user interface. Also note that a field's caption is distinct from a field's name, even if it is by default the same for the English language.
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FIELDCAPTION gives you the Caption of a field in the user's chosen UI language. This is exactly the same string that is used as a label to a control on a form that uses the field as a SourceExpression unless you changed the label's or Textbox's Caption, CaptionML or Name property. Note that this function adds MultiLanguage functionality and ensures a consistent user interface. Also note that a field's caption is distinct from a field's name, even if it is by default the same for the English language.