Job shadowing is a career exploration activity that offers students an opportunity to spend time with a professional currently working in a student's field of interest, (rather than simply hearing from academics who are in many cases far removed from the day to day of the industry they teach about.) The experience offers students a chance to see what working at a specific job is actually like, ask questions, and make professional connections. Many programs actually require job shadowing hours.
This is a great experience to consider for students who haven't yet declared a major, students who know exactly what they'd like to do, and students who aren't sure if they made the right major choice.