A Sim is a virtually simulated person. Sims are the primary focus of The Sims series, and are considered the main life state in nearly every game in the series.
Sims are complex creatures, capable of desires, fears, and physical and mental needs. Sims can have a unique appearance with different hair and eye colors, skin colors, body sizes, and more. A Sim's personality is equally as complex, with Sims having their own aspirations or traits, allowing for countless variations between Sims.
Sims live out their day-to-day lives, while also living out a full life cycle, stretching from birth to death. The progress of a Sim's life is inexorably tied to the decisions of the player; while Sims may be provided with certain amounts of autonomy, ultimately their lives are under the control of the player. This bond between player and Sim is symbolized by the Plumbob, which shows the Sim that is currently under the player's active control.