Distortion of the Torah

> And indeed, there is among them a party who alter the Scripture with > their tongues so you may think it is from the Scripture, but it is not > from the Scripture. And they say, "This is from Allah," but it is not > from Allah. And they speak untruth about Allah while they know. (Ali > 'Imran : 78) What does it mean to distort with "tongues"? You can only distort what is true. Does this verse mean that the Torah is true? And why does the distortion come only with tongues, and not with hands? What does it mean?