This document defines and explains different types of costs including real costs, opportunity costs, money costs, explicit and implicit costs, accounting and economic costs, and fixed and variable costs. Real costs refer to the physical inputs like labor, materials, and tools used in production. Opportunity cost is the value of the next best alternative use of resources. Money cost is the monetary expenditure on inputs. Explicit costs are actual payments while implicit costs are imputed values. Accounting costs differ from economic costs by excluding the entrepreneur's profit. Fixed costs remain constant while variable costs vary with output.