There are a variety of different corporations worth discussing. They are referred to as horizontal, vertical conglomerates. These are corporations that have purchased the component businesses that make their product. These are corporations that have purchased competing companies in an attempt to eliminate the competition and gain market share. It would be like IBM purchasing Compaq, Dell and Gateway.
Some horizontal mergers are illegal and are halted.
Conglomerates - This is when one company buys other companies that are unrelated to their core business in an attempt to diversify. Corporations may become conglomerates after becoming very large through mergers and acquisitions of a variety of businesses. Diversification is one of the main reasons for conglomerate mergers. By having component businesses each making unrelated products, the overall sales and profits will be protected. For example, isolated economic events, such as bad weather or the sudden change of consumer tastes, may affect some product lines at some point, but not all at one time.