It is an expression used to emphasize the truthfulness of a statement. It is similar to the English expressions "indeed", "absolutely", or "that's right".
Here are some examples of how "si vrai" can be used:
* "C'est si vrai!" (That's so true!)
* "Il a dit quelque chose de si vrai." (He said something so true.)
* "Votre analyse est si vraie." (Your analysis is very true.)