Travelers may be categorized in three ways domestic tourists, inbound tourists and outbound tourists according to the World Tourism Organization. So domestic tourism may be defined by two of these. Domestic visitors are people who are residents of a country, but travel to another part of the same country for holidays and stay from one night, up to a year. Those on day trips, or excursionists, visit an area within their own country for a day and return by nightfall. Both of these types of tourist are traveling for the purpose of leisure or fun, not work. In the Year 2000, more than a million domestic tourists traveled Cambodia. This constitutes about a twelfth of the population, and almost double the number of international tourists.

Phnom Penh residents are probably the most prolific domestic travelers. They may stay the weekend in Kampong Som or Siem Reap, for instance, or visit places of cultural, historical or aesthetic interest in nearby provinces such as Takeo or Kampong Speu. However, last year's Water Festival brought around two million domestic visitors to Phnom Penh for the three days of boat racing and partying. Domestic tourists are important for the Cambodian economy in several ways. Local people on day excursions open up new areas to tourists, local and domestic, who follow. They are the ones who "discover" new destinations, such as waterfalls and caves, and make them accessible to those who follow.

This also creates infrastructure because when domestic tourists begin to visit a place with frequency, vendors move in to service the new industry and eventually better roads and other facilities will follow. Domestic tourism plays a vital role in generating employment and reduces unemployment rates. It has a trickle-down effect on local economies, creating new business opportunities and thus improving the living conditions and reducing poverty levels amongst local residents. Worldwide, domestic tourism represents about 80 per cent of the total tourism market. In developed countries, domestic tourists can take advantage of more paid holidays, better overall rates of pay and better infrastructure. However, even in developing countries, despite people typically having less expendable income and fewer paid holidays, domestic tourists play an important role in developing the tourist economy. Domestic tourism is vital in Cambodia’s overall tourist trade.