A college seminar is a discussion. It is different than a lecture because lectures may have upwards of 100 or 200 students and lectures are smaller, typically up to 20 students. The purpose of a college seminar is to have a course discussion. Professors may assign readings to prepare before class and the entire time of the seminar is a time to discuss the readings out loud as a class. Professors may also bring in guest speakers to these seminars.
A freshman seminar is generally a class that all first-year students are required to take. Many universities have made this a requirement for student in their first year to help them succeed in college. In the class they teach you about success strategies. Some universities even have their freshman seminar separated by major. Its primary purpose is to help students transition from high school into their first year of college. It is also known in some as the First Year Experience (FYE).