Best Answer I got all of this from wikipedia...
Sims are also able to level up in new skills; Photography, Martial Arts, and Nectar Making. In addition the game provides new objects, socials, wishes and opportunities.
Opportunities, are 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. Career opportunities such as working overtime or completing special tasks can yield a pay raise, cash bonus, or relationship boost. Skill opportunities are requests by neighbors or community members for Sims to solve problems using their acquired skills for cash or relationship rewards.