Internships provide on-the-job training similar to apprenticeships. Some high school programs such as California Partnership Academies include internships as part of their required experiences, but they can also be found by an individual student.
Internships are opportunities to gain experience in a particular type of work. You can determine if you have an interest in that particular career, you can create a network of contacts, and/or gain school credit. Internships provide employers with cheap or free labor for (typically) low-level tasks. Some interns find permanent, paid employment with the companies in which they interned. Their value to the company may be increased by the fact that they need little to no training.
Internship positions can be found in most occupational areas including business, government, non-profit groups, and organizations.
Check with your school counselor, work experience coordinator, and/or teacher to learn if your school has an internship program.