The Sims 3 differs in several fundamental ways from its predecessors:
Sim houses and neighborhoods are entirely in one continuous map.
The Sims 2 used a reward system called Wants and Fears. This is replaced with a new system called Wishes in The Sims 3. Fulfilling a Sim's wish contributes to the Sim's Lifetime Happiness score and mood.
The game includes an optional feature called "Story Progression," which allows all Sims in the neighborhood to autonomously continue as if the player were controlling them, such as grow up, get married, get jobs and promotions, have children, build or buy their dream house while the player isn't playing.
Opportunities, tasks that Sims can complete to earn rewards. These challenges occur randomly based on aspects of each Sim's lifestyle, such as relationships, skills and job.
In addition there are many improvements to building and shopping tools, as well as new careers and skill bonuses.