Online discussion forums are crucial educational tools that facilitate interaction between students and teachers. We created an online discussion forum, with the teacher serving as the moderator. 58 posts and 1,955 comments were collected. We analysed these data through Latent Dirichlet Allocation to determine word cooccurrence and extract key topics from the discussions. We examined how the topics and depth of the discussion changed over time and the roles that the students and teacher played in the forum by using time-series data. The results indicate that the teacher played a crucial role in the forum by initially serving as a moderator and then guiding or prompting students to discuss certain topics. Those who participated more actively achieved higher grades, and those that were passive had lower grades at the end Overall, the online discussion forum enhanced the course by helping students understand the core materials and topics in the course.