Tourism is travel for pleasure, and the commercial activity of providing and supporting such travel.UN Tourism defines tourism more generally, in terms which go "beyond the common perception of tourism as being limited to holiday activity only", as people "travelling to and staying in places outside their usual environment for not more than one consecutive year for leisure and not less than 24 hours, business and other purposes". Tourism can be domestic (within the traveller's own country) or international. International tourism has both incoming and outgoing implications on a country's balance of payments.

Between the second half of 2008 and the end of 2009, tourism numbers declined due to a severe economic slowdown (see Great Recession) and the outbreak of the 2009 H1N1 influenza virus. These numbers, however, recovered until the COVID-19 pandemic put an abrupt end to the growth. The United Nations World Tourism Organization has estimated that global international tourist arrivals might have decreased by 58% to 78% in 2020, leading to a potential loss of US$0.9–1.2 trillion in international tourism receipts.

Globally, international tourism receipts (the travel item in the balance of payments) grew to US$1.03 trillion (€740 billion) in 2005, corresponding to an increase in real terms of 3.8% from 2010. International tourist arrivals surpassed the milestone of 1 billion tourists globally for the first time in 2012. Emerging source markets such as China, Russia, and Brazil had significantly increased their spending over the previous decade.