Tourism is comprised of the activities of one travelling to, and staying in, places outside their usual environment (I have read the statistic of 50 or 80km) for no more than a certain amount of time (I have read 28 days, or a year) for leisure, business, education, and/or other purposes.

However, the act of travelling outside of one's usual environment, and not staying, is sometimes classified rather as recreation, or "day-tripping", and not tourism. Where some believe that tourism is limited to travel for the purpose of leisure, others believe that it can encompass all non-commuting related travel, thus being the art, science and business of attracting, transporting, accommodating, and catering to the desires of people.

If tourism is seen as the sum of these relationships, and requires the interaction of governments, communities, businesses, and tourists, the Liberal argument is that this might be an economic solution to the attainment of world peace. But within western culture, tourism has come to symbolize both a pilgrimage, the sacred journey of discovering one's self, and imperialism, where those who have may visit those who have not, and not the inverse.
In economics, tourism refers to spending before, during, and immediately after such a trip. No matter the perspective, it is generally agreed upon that, if tourism is an industry, it is the largest one in the world. Five general, identifiable classifications of tourism:

Domestic tourism is where resident visitors within the economic territory of a given country tour or travel.
Inbound tourism is where non-resident visitors do the same.
Outbound tourism is the opposite, where residents of a given country tour or travel outside its economic territory.
Internal tourism is the sum of residents' and non-residents' touring or traveling in a given country's economic territory.
National tourism is the sum of residents of a given country touring and traveling both within and without its economic territory. Specific forms of tourism:

Agricultural Tourismis travel to any operating agricultural, horticultural or agribusiness operation, for limo company nyc the purpose of enjoyment, education, or active involvement in the activities of the farm or operation.
Rural Tourism is travel to rural settings or environments for the purpose of experiencing activities, events, and attractions not readily available in urbanized areas, though not necessarily agricultural in nature.
Sustainable tourism is the notion of tourism serving the dual purpose of maintaining the cultural integrity of the host region, and protecting local ecology and biological diversity while achieving the economic, social and aesthetic needs of the visitor.

Ecotourism, as defined by The International Ecotourism Society website is "responsible travel to natural areas that conserves the environment and sustains the well-being of local people, while providing a quality experience that connects the visitor to nature." Ecotourism places further emphasis than sustainable tourism on the learning experience, on maintaining small travel groups, and on local ownership of visited sites.

Heritage tourism: is responsible travel to historic and cultural sites, and involvement in activities that educate both the visitor and the community through the connection to the area's customs, values, beliefs, art and artifacts. Heritage tourism tends to place more emphasis on the geography than the society.

Cultural tourism, is travel to experience the cultural, historic, and natural places, artifacts, and activities which authentically represent the stories and people of the past and present. Cultural tourism thends to place more emphasis on the society than the geography.