An acquisition occurs when one company takes ownership of another company by purchase. There are four main types of acquisitions: friendly acquisitions involve mutual agreement between companies; reverse acquisitions involve a private company purchasing a public one; backflip acquisitions result in the purchasing company becoming a subsidiary; and hostile acquisitions are done against the will of the target company. Acquisitions allow companies to increase market share and diversification but can also overleverage acquiring companies with debt if not properly valued or integrated.