Synonyms: Linguist, Multilingual
In most situations, the players are either talking to a learned men, in which case they speak in Latin or they are in a region speaking one of the main languages and hence can communicate.
But in remote corners of Europe, such as Ireland, Isle of Man, the Sultanate of Grenada, the Pagan far East, etc, the local illiterate populations only speak a local language.
In which case the players can hire a translator, but cannot communicate directly with locals, hence being unable to use any communication based skills such as Detect Lies.
Using this Feat you are miraculously able to speak almost any languages and can use any communication based Feats directly on any illiterate local.