Talking to Chuck and asking for his advice leads to him doing a Tarot reading for the Vault Dweller. By getting various "fortunes", Chuck will place markers on the world map for the locations.
He'll give the Vault Dweller between one and three readings for locations: the Brotherhood (if the Vault Dweller never had anyone mark it), the military base (if the Vault Dweller has not been there or found its location in the Cathedral vault), and finally the Cathedral (always).
Next time after that he'll draw the fool card and the Vault Dweller's Luck will go up permanently by 1.
Mocking his fortunetelling will result in him getting offended and refusing to read the Vault Dweller's tarot.