The document defines different types of costs including total fixed cost, total variable cost, total cost, average fixed cost, average variable cost, average cost, and marginal cost. It provides examples of costs that are fixed (rent, insurance, salaries) versus variable (direct labor, energy, raw materials). It also discusses cost estimation and different models used for cost estimation like the learning curve model, segmenting model, per unit model, cost index model, power sizing model, and break even quantity model.