Holding company ( H ) means a company having more than 50% of the holding of another company's shares. That company is then a sunsidiary ( S ) of the holding company.
H is also regarded as a holding company if the board of directors of H has a significant or dominate power over the decision making of the board of directors of S. It is usually the case the majority of the directors of S are coming from H. So, any resolution made by the Board of Directors of S is controlled by those directors coming from H.
You may also noted that there is a name called - the ultimate holding company. It means H holds B and B holds C. From the point of C, the ultimate holding company is H and B is only the immediate holding company.
Not all listed companies are ultimate holding companies. They are usually holding some subsidiaries.