Confidential Participants are hidden to any staff member that does not have access to that confidential Program. Their information recorded in ETO will also not show up in reports.
The only difference between Find Participants (C) and Find Participants is that Find Participants(C) will exclude the information on confidential Participants. When you have confidential Programs, you will want to only give users access to Find Participants (C).
If you do not see Find Participants (C) on the Navigation Bar, you can add it by going to Manage Site Navigation under Site Administration on the Navigation Bar.