Cost management is the process of planning and controlling a project's budget to help ensure the project is completed within budget. It involves estimating costs, setting a budget baseline, tracking actual costs against estimates, and implementing controls to address any variances. Key aspects of cost management include cash flow analysis, distinguishing direct and indirect costs, earned value analysis to measure performance, and using tools like cost management plans, cost accounting, and earned value reports in Primavera and Microsoft Project to help manage costs over the life of a project. The overall benefits are keeping the project within its approved budget, having accurate cost forecasts, and maximizing return on investment.