This is mostly done by students who are in their final year. With this kind of internship a student does research for a particular company. The company can have something that they feel like they need to improve, or the student can choose a topic within the company themselves. The results of the research study will be put in a report and often will have to be presented. Students can gain experience by working with the development team. Research internship is usually unpaid in European countries.
Sources:
http://www.altimetergroup.com/about/careers/research-intern
https://www.training.nih.gov/programs/sip