What is the difference between Conference,seminar and symposium ?

Conference: 1. A meeting for consultation or discussion.

Seminar: A meeting for an exchange of ideas; a conference.

Symposium: A meeting or conference for discussion of a topic, especially one in which the participants form an audience and make presentations.

In short, a conference is any meeting of a group of people on a particular general topic (computer networking, business law, etc).

A seminar is usually a smaller gathering (and often conferences have seminars within them), generally considered more "intimate," concentrating on a specific topic (Contract Law, specifically breach of contract, as an example). Often audience members are able to directly interact with the presenters, asking questions, etc...

A symposium is similar to a seminar, except the presenters often form the audience, as well. Example: a bunch of lawyers get together, each making a presentation on a different topic.

All seminars and symposiums are types of conferences. Not all conferences are seminars or symposiums.