As a student or member looking to make a booking, you may have seen "Busy" in the booking form. When you see this, it means someone has booked these slots, and they have not opted in to be contacted by other members.
If you see someone's initials, they are opted in and you can send them a message via the system. So if you opt in to being contacted, your initials will appear in the bookings. Other users can click your initials to send you a message via the system. Your personal details are not shared with other users; ticking the box only shows your initials and allows the system to relay emails to you from another user.
If you would like to opt in, you'll find the preference in your account under Personal data. Just put a tick in the box!