The document discusses the concept of cost of capital, defining it as the price incurred by a company to borrow money or attract investment, which includes components like return at zero risk, business risk premium, and financial risk premium. It categorizes cost of capital into various types, such as historical vs. future costs and specific vs. composite costs, and outlines methods to compute the cost of different capital sources like debt, equity, and retained earnings. Additionally, it introduces Weighted Average Cost of Capital (WACC) as a crucial financial metric in decision-making, including detailed formulas for calculating specific and composite costs.