A “Phrase” is not an Object but a “struct” that is embedded in an Object or used on the stack.
It points to something and provides a length.
It is typically used to point to text, such as in a Clause.
It allows for use of part of the text without the need to make another copy in a Clause or String.
It is has fast parsing functions that will extract another Phrase from a given one, possibly modifying the original Phrase, while the data pointed to remains unchanged.