Fair, Expo, Conference

What's the difference between these on the Outings page? Expo and Fair sounds similar then why two separate entries? And what’s this Conference anyway?

(Expo)sition: showcase a wide range of coins, currency and related items (often rare items and educational activities); open to the public and all types of collectors; large-scale 

Fair: mainly for commerce purposes; attracts from casual collectors to dealers; usually on a smaller scale and more local

Conference: for scholarly or professional numismatic exchange of knowledge; attendees are scholars, museum curators and serious specialised collectors; usually smaller and very specialized