You can then collect them back if you desire (say, for an exam or questionnaire). If you choose, project your screen as a slideshow on your students' Macs so that everyone sees you as you instruct without them having to do any login or other action. Find a specific computer quickly and control it if they need your help. Imagine giving a talk with colleagues, distributing a file and then later once they save their work being able to collect it, as if by magic, into a portfolio without them having to use a file share, or e-mail. Each file can be marked up or graded and sent back to the student.