Each character has 5 different stats (or traits): Geek, Artist, Romantic, Charmer, and Jock. Each character starts with a predominant stat, you can raise the other stats by doing quests or by using different costumes. You can see the stats for each character in the Character Info button in the Options section.

For example, Jasmine's main trait is Charmer but if we use a different type of outfit on her we can increase her Geek stats instead.