Demand forecasting involves estimating future demand for a product or service based on past data and consumer behavior analysis. There are several types of demand forecasting including passive, active, firm-level, industry-level, and national-level forecasting. Common demand forecasting methods include surveys, expert opinions, sales force opinions, and market experimentation. An effective forecasting method should be simple, accurate, economical, flexible, and able to provide quick results. Demand forecasting is important for business planning, budgeting, management decision making, and evaluating performance.