Seminars and workshops can both be meetings on a particular topic. Seminar implies listening to people speak. Workshop implies hands on activity. For example: a seminar for writers could include writers giving presentations on their creative process or publishing. A workshop for writers would probably involve sharing and discussing writing samples, or helping people write a publishing proposal.

There are various types of seminars but typically they are a gathering of people to exchange ideas on a topic/area of interest. They typically have lectures and workshops. A workshop is technically something very different. You actually get them at seminars. A workshop is a group of people who come together to work together. All participants are normally active and taking part in the activity i.e. it is a gathering to get work done. so for example a lecture is typically 1 person talking to many. one type of workshop is a teacher/instructor who supervises/helps as all member try to work through something. There are other types of workshops though as well.