A sector is one of a few general segments in the economy within which a large group of companies can be categorized. An economy can be broken down into about a dozen sectors, which can describe nearly all of the business activity in that economy. For example, the basic materials sector is the segment of the economy in which companies deal in the business of exploration, processing and selling the basic materials such as gold, silver or aluminum which are used by other sectors of the economy. Sectors also often have specific ETFs that track sector such as the Energy Select Sector SPDR Fund (XLE)
