Incentives exist in many forms. For some it is the opportunity for promotion and increased salary. For others it is a great dental plan or a month of paid vacation.
In all cases, incentives are used to make employees feel appreciated and valued.
Money is the more commonly used form of incentive. Most people tend to think that money is the main determinant of Job Satisfaction. This is not necesarily true: many surveys have shown that managers with high salaries are often on average less satisfied than the people they manage.
Other issues regarding money may have more impact on a person's satisfaction, such as a fair distribution of pay among employees with equal responsabilities.