Contextual inquiry is an ethnographic research method where users are observed and questioned in their natural work environments. It involves briefly interviewing users, observing them without interrupting as they work, and summarizing insights with them. Key principles are conducting the inquiry in the actual work context, collaborating as partners to understand the user's work, sharing interpretations with the user, and focusing on relevant topics. Researchers should be likable to put users at ease, avoid audio/video recording, and capture artifacts like photos or notes.