This document defines cost-benefit analysis and outlines its key steps and applications. It begins by defining costs and benefits. It then explains that cost-benefit analysis is a systematic approach used to assess the strengths and weaknesses of alternatives by comparing total expected costs versus total expected benefits. The document lists the main steps of cost-benefit analysis as: 1) specifying the project clearly, 2) describing quantitative inputs and outputs, 3) estimating social costs and benefits, and 4) comparing benefits and costs. It also discusses some principles and applications of cost-benefit analysis.