Semi-structured interviews are interviews where you have a list of general topics or questions to guide the conversation, but you also allow for flexibility and adaptation. They are often used for exploring opinions, experiences, or motivations, or for gaining a deeper understanding of a phenomenon. The main advantages of semi-structured interviews are that they are more natural, engaging, and responsive than structured interviews. They enable you to follow up on interesting points, clarify ambiguities, and tailor the questions to each participant. They also allow for more creativity, spontaneity, and discovery in the interview process. However, semi-structured interviews also have some challenges. They require more skill, preparation, and rapport from the interviewer. They are harder to standardize, compare, and quantify. They may also introduce more variability, subjectivity, and bias in the data collection and analysis.