A Player Character ("PC") is a character that a player controls in a role-playing game.
The typical adventure in a typical RPG system is written for a party of four to six player characters of a consistent power level and assumes that each character can handle at least one role considered "traditional" for the setting (e.g. physical or magical combat, stealth, interaction, and deciphering puzzles).
Player characters, depending on the system and thematic elements in use, are known for immortality, grand powers, destruction, healing, wealth, poverty, unearthing secrets best left forgotten, plot armor, and many other things.
Generally good people for NPCs to avoid.