An internship is an agreement between you and a company or organization for a fixed period of time, such as a semester or quarter. You agree to work for them and they agree to mentor and teach you; internships can offer valuable insight into a particular field or career. Many internships are organized through colleges and high school programs. Many companies go on to hire their successful intern's full time.
A student gets to learn ample amounts from an internship, be it the work, the work culture, the experience, the office atmosphere etc.

When choosing any course, be aware that if the internship is not completed then neither is the course is also completed.

Note : Not all internships are paid. Some of them are also unpaid. Always make sure to find out whether an internship is paid or unpaid.