The basic definition of special groups is those employees of strategic value to a company, who therefore have compensation packages consisting of more than the common, basic hourly wage. In a sense, they can be defined as systematically important employees.
The first group is the Board of Directors, who are not regular employees, but who answer directly to shareholders. Outside or independent directors are normally compensated with a mix of a stipend, equity, and other benefits including liability insurance.
Next, executives and upper management are considered systematically important to a company, and normally receive a complex compensation package including base salaries, stock options, bonuses, "golden parachutes", and other incentives.
Sales people often work on commission or a combination of salary and commission.
Especially in technology, entertainment, and other field in which revenue is based on creativity and innovation, employees such as film directors, scientists, or other key creative or technical people form a special group. These people may be compensated by a mix of salaries and royalties, as well as stock options and bonuses.