This a Type-Specifier function. It takes a text parameter and simply returns it. Its primary use is when you want to ensure that a data reference or prompt value is treated as being of type text, in contexts where its role might otherwise be ambiguous. You can also use it as a 'wrapper' to contain other concatenated text expressions - see the example below.
=Text(%INDI% . " married " . %INDI.~SPOU>%)