A convention is a meeting of individuals who meet at an arranged place and time to discuss or engage in some common interest. The most common conventions are based upon industry, profession, and fandom. Trade conventions are usually about an industry or industry segment. They often include keynote speakers, vendor displays, and other information and activities of interest to the event organizers and those who attend the convention. Professional conventions focus on issues of concern to the profession. Fan conventions usually feature displays, shows, and sales based on pop culture and guest celebrities. Science fiction conventions are similar to both professional conventions and fan conventions. Conventions also exist for various hobbies, such as gaming or model railroads.