Skill: Diplomacy
Diplomacy is the act of influencing others through negotiation, flattery, or wise use of words. It can be used to find information through friendly chats, or influence other creatures (both Humanoid and not). One can even use it to do turn entire plots on their head. To this end, Diplomacy and talents based around such focus on using Wisdom or Charisma, being a mental stat that focuses on a character's proclivity to being social.
Mechanically, Diplomacy will be the primary skill called on to influence creatures and/or make a case for themselves. The DC will often be based around the situation, and/or will be determined by the GM and/or the adventure.
Diplomacy uses WIS / Wisdom or CHA / Charisma by default. Diplomacy is a Primary Skill, meaning it is a major skill that can only be gained by mechanics that grant proficiency.