Player character
A player character is a character in a role-playing game that represents one of the players. When you start an RPG, you usually create a character. Most RPGs, such as Dungeons & Dragons, have a system for the creation process with intricate rules and many choices. Such RPG element is also largely known as avatar. However, the character's attributes don't need to correspond to the ones of the player. In most RPGs, people usually have freedom to create any kind character. An avatar is a representant for the player within the game enviroment, yet it doesn't need to refrect his personality.The player character takes the place of the actual player in the game. The character has detailed characteristics, from the important (endurance, strength, etc.) to the trivial (favorite color, height).
It is generally a good idea to not play the stereotypes unless it is required. They get boring after a while for most people. Usually a character that has little quirks - a three-dimensional character who's as complex as anyone you know - is more interesting.
A player character provides the player a chance to be wild, to do things that could never be done in reality. Of course, one stay within the limits of believability in the game. A good idea is to ask one's gamemaster for more details.
In contrast to player characters, a non-player character (NPC) is a character in an RPG that is not controlled by one of the players.