For guidance on visas for those individuals who wish to visit the UK, see the University's pages here: http://www.hr.admin.cam.ac.uk/hr-services/immigration/visitor-administration.
For guidance on visas that will allow individuals to work as an employee, see the University's pages here: http://www.hr.admin.cam.ac.uk/hr-services/immigration/visas-and-right-work-uk/time-limited-right-work.
Students attending organised short courses of study, such as summer schools, at the University of Cambridge can do so on a short term study visa. Students must not enter the UK on a standard visitor visa for the purpose of attending these courses.