What's the difference between Cons and japan's festival?

Festivals are primarilly used to celebrate something. Like the Cherry Blossom Festival or Summer Festivals.

Conventions are used as a gathering of people who share the same interests such as anime, cars, technology. Ususally you get the people together have events, discussions, and what not.

Yup, and cons have people dressed up as anime characters where as festivals have people dressed in traditional clothing and such.

@naota : but at my place. the the festival always be held with another interest. so i can't tell how exact it was a convention one like you told or it was a celebration of an event like cherry blossom festive or another example.

but, at my place, we are rarelly don't have any convention event. its just a toys fair ( not a comic) who used as event for gathering people.

@maria: in my place, that's the opposite. i don't know who or how it will end like that. sometimes when it was a festival, people going to wear any japanese cosplay chara (well, there is some yukata also) but, it doesn't suits with the event though.. am i right?