Tourism refers to the act of travelling for pleasure or commercial purposes. In addition to the concept and practise of travel, tourism includes both the business of attracting and welcoming tourists, as well as the business of organising and conducting tours. According to the World Tourism Organization, tourists are people who "travel to and stay in locations outside their normal surroundings for not more than one continuous year for pleasure. According to the World Tourism Organization, this definition goes "beyond the conventional notion of tourism as being confined to vacation activity alone," and encompasses a wide range of activities. In terms of character, tourism may be classified as either domestic (inside a traveler's own country) or international in nature, with international tourism having both incoming and outgoing effects on a country's balance of payments. Domestic tourism is defined as tourism that takes place within the traveler's own country.
During the second part of 2008 to the end of 2009, tourism numbers fell as a result of a severe economic downturn (the late-2000s recession) and the emergence of the 2009 H1N1 influenza virus, but steadily rebounded until the COVID-19 pandemic put an abrupt halt to the recovery. International visitor visits may decline by 58 percent to 78 percent in 2020, according to the World Tourism Organization of the United Nations, resulting in a possible loss of US$0.9–1.2 trillion in international tourism revenues by 2020.
In 2012, international visitor visits exceeded the 1 billion mark for the first time in history, with rising source markets such as China, Russia, and Brazil having substantially boosted their expenditure over the preceding decade.
World tourism is responsible for about 8% of global greenhouse gas emissions. Environmental and social consequences of emissions, as well as other major environmental and social consequences, are not necessarily advantageous to local people and their economy. As a result, many tourism-related organisations have started to place greater emphasis on sustainable tourism in attempt to minimise the negative consequences of the increasing influence of tourism on society. Tourism as a component of the Sustainable Development Goals was promoted by the United Nations World Tourism Organization through programmes such as the International Year for Sustainable Tourism for Development in 2017 and programmes such as Tourism for SDGs, which focused on how SDG 8, SDG 12 and SDG 14 are implicated in the creation of a sustainable economy.