Market research involves collecting, analyzing, and understanding data related to markets and customer behavior. It is used primarily by manufacturing, service, and retail companies to guide decisions around new products, marketing, and sales. Most large businesses conduct both internal and external market research, spending 1-2% of revenue on average. There are different types of market research including primary data collection, secondary data analysis, qualitative research like focus groups, and quantitative research using surveys. Proper sampling techniques and question design are important to obtain accurate and unbiased insights.