Supervisory board

A supervisory board or supervisory committee, often called "board of directors", is a group of individuals chosen by the stockholders of a company to promote their interests through the governance of the company and to hire and supervise the executive directors and CEO.
Corporate governance varies between countries, especially regarding the board system. There are countries that have a one-tier board system (like the U.S.) and there are others that have a two-tier board system like Germany.
In a one-tier board, all the directors (both executive directors as well as non-executive directors) form one board, called the board of directors.
In a two-tier board there is an executive board (all executive directors) and a separate supervisory board (all non-executive directors). The chairman of the supervisory board is the equivalent of the chairman of a single-tier board, while the chairman of the management board is reckoned as the company's CEO or managing director. These positions are almost always held by separate people.
Germany.
German corporation law, the "Aktiengesetz", requires all public companies ("Aktiengesellschaften") to have two boards:
a management board called a "Vorstand" and a supervisory board called an "Aufsichtsrat". The supervisory board oversees and appoints the members of the management board and must approve major business decisions.
For German companies with more than 2,000 employees, half of the members of the supervisory board are elected by the employees. When a German company has between 500-2,000 employees, the workers select one-third of the supervisory board.
When it comes to internal elections the chairman of supervisory board, the "Aufsichtsratsvorsitzender", has two votes in case of a draw.
The supervisory board, in theory, is intended to provide a monitoring role. However, the appointment of supervisory board members has not been a transparent process and has therefore led to inefficient monitoring and poor corporate governance in some cases (Monks and Minow, 2001).
The discussion about whether a one-tier or a two-tier board system leads to better corporate governance is ongoing in Germany and many other countries. 
China.
Another example of a two-tier board system: Mainland China
In China's corporation law, the so-called (中华人民共和国公司法), it stipulates a limited liability company (有限责任公司) to have: a board of directors (董事会) and a board of supervisors (监事会).
Regarding the Chinese requirements of a board of supervisors, under Articles 52 to 57 of the Company Law of the People's Republic of China: