An industry is a group of manufacturers or businesses that produce a particular kind of goods or services. Workers in the textile industry design, fabricate, and sell cloth. The tourist industry includes all the commercial aspects of tourism.
You can use industry to refer to a group of similar businesses: The automobile industry makes cars and car parts. The food service industry prepares food and delivers it to hotels, schools, and other big facilities. Industry comes from the Latin industria, which means "diligence, hard work," and the word is still used with that meaning. If you build a house in three weeks, when the same job takes everyone else three months, you're showing impressive industry.