A convention, in the sense of a meeting, is a gathering of individuals who meet at an arranged place and time in order to discuss or engage in some common interest. The most common conventions are based upon industry, profession, and fandom. Trade conventions typically focus on a particular industry or industry segment, and feature keynote speakers, vendor displays, and other information and activities of interest to the event organizers and attendees. Professional conventions focus on issues of concern to the profession and advancements in the profession. Such conventions are generally organized by societies or communities dedicated to promotion of the topic of interest. Fan conventions usually feature displays, shows, and sales based on pop culture and guest celebrities. Science fiction conventions traditionally partake of the nature of both professional conventions and fan conventions, with the balance varying from one to another. Conventions also exist for various hobbies, such as gaming or model railroads.