The origins of world's fairs lay in a French tradition of national exhibitions, and the success of the French Industrial Exposition in 1844 lead to the adoption of such events by neighbouring European countries. The idea made its way to the United Kingdom, which held the "Great Exhibition of the Works of Industry of All Nations", better known as simply "The Great Exhibition", in 1851. This event set down the precedent in terms of scale and content, which expanded beyond a single topic and included exhibits on wider aspects of society, including art-and-design education, international trade and relations, and tourism. This format was later copied by several other cities in the 19th and early 20th centuries, such as Paris, who held numerous world's fairs.

The rising popularity of the world's fair concept brought conflicts of schedule and interest. In 1928, a convention to schedule regular World's Fairs was created, and the BIE was created to coordinate World's Fair organization. Soon after, the themes that typified world's fairs began to change. An international exhibition in New York in 1939-40 began a shift from the unveiling and showcasing of new technologies and practices to exhibits relating to human and cultural experiences. This paradigm continued after the Second World War, and term 'Expo' for world's fairs was coined in 1967 at Montréal's International and Universal Exposition, or Expo 1967.

Eventually, the idea that world's fairs were a great vehicle to advertise countries became prominent, and the pavilions began to carry greater cultural and historical references to the countries that displayed them. Today, world's fairs employ not only nation branding, but throwbacks to the old paradigms of world's fairs, showcasing new and innovative technologies, and reflections on the prevailing human condition and experience.

There are three types of world's fair as set out by the BIE:

• Universal Expositions (World Expositions) are the largest expositions and are considered the 'major' fairs. These events take place every five years and last anywhere between three weeks and three months. They are the most expensive and often most extravagant type of fair, as large international participation requires enough area for each country to promote their national brand. Participants are required to build their own pavilions. This means no expense is spared, often resulting in some spectacular exhibits. Themes are usually universal to the human experience. All events of a suitable scale prior to 1928 were retrospectively made Universal Expositions. Expo 2020 in Dubai, United Arab Emirates, has been postponed to 2021 due to the COVID-19 pandemic.
• International Expositions (Specialized Expositions) are the smaller than Universal Expositions, and are considered the 'minor' fairs. These events tend to encompass much narrower or specialised themes. There is no set frequency to these events, although only one may be held in the five-year gap between the larger Universal Exhibitions.
• International Horticultural Expositions are specialised events which showcase floral displays, botanical gardens and anything else to do with plants. Although in theory they can take place annually (so long as they are in different countries), in practice they are not. These events normally last anywhere between three and six months, and are held on sites no smaller than 50 hectares. They are jointly sanctioned by the BIE and the International Association of Horticultural Producers (AIPH). The 2019 event was held in Beijing, China.

The BIE also recognizes the Milan Triennial Exhibition of Decorative Arts and Modern Architecture (also Triennale di Milano, Milan Triennale, or Triennale di Milano International Exhibition) for historical reasons, provided that it retains its original features. The Triennale showcases modern decorative and industrial arts. In 2019, the XXII Triennale focused on design approaches that explore the relations between humans, nature and other species.

• Internationale Gartenausstellung 2017 (IGA 2017), a Horticultural Exposition, in Berlin, Germany, ran from 7 April to 6 October 2017.
• Expo Astana 2017, an International Exposition in Astana,Kazakhstan, ran from 10 June to 10 September 2017, with theme Energy of the Future.
• XXI Triennale International Exhibition, in Milan, Italy, ran from 2 April to 12 September 2016 with theme 21st Century. Design after Design.
• Expo 2016, a Horticultural Exposition in Antalya, Turkey, ran from 23 April to 30 October 2016, with the theme A Green Life for Future Generations.
• Expo Milan 2015, a Universal Exposition in Milan, Italy, ran from 1 May to 31 October 2015 with the theme Feeding the planet, energy for life.
• Expo 2012 (2012 여수 세계 박람회 International Exposition Yeosu Korea 2012) was an International Exposition held in Yeosu, South Korea. The theme of the event was 'The Living Ocean and Coast', and it ran for three months, from May 12 - August 12, 2012. Expo 2012 received over 8,000,000 visitors and was attended by 103 countries and 8 international organisations.
• Floridae 2012 was the most recent instalment of the Netherlands' decennial flowering and gardening exhibition, the sixth time it was sanctioned by the BIE and AIPH as an International Horticultural Exposition. Held in the southeastern city of Venlo, the theme of the event was 'Be part of the theatre in nature; get closer to the quality of life'
• Expo 2010 ((上海世博会 Shanghai Shibohui), a Universal Exposition, was held in Shanghai, China. The theme was 'Better City – Better Life', focusing on urban development. The event ran for 184 days, opening on May 1 and closing on October 31, 2010. World fair attendance records were broken, with more than 73,000,000 overall visitors over the six months, including more than 1,000,000 visitors on October 16 alone. Over 180 countries participated in the event.