What is a divestiture, and why would a company complete one?

• A merger of equals that combines two similarly sized firms under a newly created holding company
• An issuance of new stock to the public, done to raise growth capital for reinvestment in the core business
• The purchase of a competitor, undertaken in order to expand the company's product portfolio, market share, and geographic footprint
• A distribution of cash to shareholders as a dividend
• The sale of a business unit or asset, done to refocus on the core, raise cash, or shed a non-core/underperforming unit