Anonymous (recommended): recruiters see your skills and background, never your name, photo, contact details or employers' names. To contact you, they send a request; you decide whether to answer.
Public: your name and contact details show only to verified recruiters who unlock your contact. Hidden: you do not appear in the CV database; your applications stay visible to the companies you apply to.
Confidential mode and the blocked-companies list protect you from your current employer. « View as a recruiter » shows exactly what they see.