It is a good idea for students to go for internship as it helps them gain experience and knowledge about how the corporate world works, and also, they get to get a clear picture of what it is like to work in a particular field or industry and then analyze whether it is actually their true calling or not. For example: A management student can take up internship in either the finance or marketing or HR profile and get first hand experience about how these fields work, and then make up his / her mind about what field he would like to pursue his full fledged career in.
Internships not only benefit the student but also the organizations as there are many small part-time projects which require manpower. Interns can be of great use for such short term projects.
If one follows the career which matches ones inherent strengths, then they will naturally be able to enjoy their work. So if an intern takes up a part time project with an organization which is in sync with his inherent talent or strengths, then he will be able to perform well in his job, and, chances of his getting a pre-placement offer from the same organization also increases.
But many students do not know what their inherent strengths are. Or they have a miscalculated understanding their inherent strengths.