Conventions usually require one to register to gain admittance. Attendees might have to wear a badge as proof of payment. Conventions can range from one day to weekends and more, and prices vary in entrance fees.
Features of conventions might include (but not are not restricted to) events such as autograph signing, art sales, marketplaces or 'dealers rooms,' and entertainment (eg: boxing matches, karoake contests, dance contests, movie rooms, etc).
A convention is oftentimes shortened to simply a 'con,' in which case one might state that they are 'going to the con.'