The Companies Act 1956 was passed by the Indian Parliament in 1955 and came into force on April 1, 1956. It defines a company as a voluntary association of people established for business with a separate legal identity. A company has characteristics such as perpetual succession, limited liability for members, transferable shares, and management by a board of directors. The Companies Act recognizes different types of companies based on criteria such as number of members, liability of members, ownership, and control.