Tourism means people traveling for fun. It includes activities such as sightseeing and camping. People who travel for fun are called "tourists". Places where many tourists stay are called "resorts". Places that people go to for tourism are called tourist destinations.
There are a lot of reasons why people travel for fun:
Some people travel to learn about the history or culture of a city or country, or learn about the people who live there, or their ancestors.
People from cold places sometimes like to relax in the sun. Many people from the north of Europe or North America travel to warmer places and visit beaches.