"My experience of students who complete an internship return to their studies much more aware of the relevance of their study programme to the real world and much more 'streetwise' in terms of their engagement with activities and their learning." University of York academic
An internship provides you with experience of the real working world - an opportunity to explore a company, a technical area or a business sector to see if it is where you see yourself working for your first job. Along with that it can be the extended interview that gives you the offer of a full time job!
An internship also gives you a great opportunity to develop a wide range of life skills, so called generic or transferable skills - the skills that are key to your employability. The whole experience will be of great value to you for your CV and your employability.
An alternative way of looking at some internships is an opportunity to earn money for future funding of your study programme or lifestyle! Note though that not all internships are paid.
Find out some opinions of your colleagues.