A questionnaire is a research tool used to gather data and information from respondents on a specific topic or subject. It typically consists of a series of questions that are designed to elicit responses from participants, which can be used to analyze and interpret the data collected. Questionnaires can be administered in various formats, such as online surveys, paper surveys, or in-person interviews, and can be used in a wide range of research areas including psychology, sociology, marketing, and healthcare. The goal of a questionnaire is to gather reliable and valid data that can be used to address research questions, test hypotheses, and draw conclusions.