Concentration on providing particular types of goods and services, and relying on others to provide what one does not produce. This occurs at all levels: individuals acquire particular skills or professional qualifications; firms concentrate on particular industries; districts, regions, or whole countries specialize in particular activities. Specialization may be total or partial. With total specialization, goods and services used by an economic agent are entirely provided by others. This is very common at the individual and the firm level. With partial specialization, some but not all of particular goods and services are acquired from others. This is common at the regional and national level: many countries, for example, provide some but not all of their own food or fuel.