Every Sim has a life aim and dreams. They both depend mainly on the personality. Life aim is one for the whole life, dreams appear everyday. When you create Sim you may choose his or her life aim - you cannot control dreams.
Wishes are a kind of Sims' dreams. Further ones appear in a window on the left from Sim's image . Use arrows to move between active wishes of a Sim. When you want to fulfill a wish , click left button of the mouse and you will be moved to one of four fields below. If you perform well, it will be scored and disappear. You can reject - take back a wish at any time (click on it by using right button on the mouse at four fields as described before). When arrow is on a wish you can get extra information  - what you should do and how many life happiness points you will get.
Wishes can be very different. To learn particular skill or to develop it , read a book on a particular subject, get promoted, have a baby of a particular sex - there are so many, hundreds even. Fulfilling Sims' dreams, you get life happiness points [information about them are described in another chapter] and offers positive moodlets.
A separate element is a lifetime wish - the aim of Sim's life. It is presented under the character's image .
When arrow is on the icon, you will get information what you should do . There are many wishes: to achieve a particular level of career, make a certain number of money, obtain the highest level of a particular skill (or even two), see a ghost of a rich Sim, be a boyfriend/girlfriend of a certain number of Sims, achieve 5th level in four different careers, make friends with a certain number of Sims etc. After fulfilling lifetime wish the background of the icon will change , and you will get really many life happiness points.