Participant role is given to everyone once they are added to a workspace as users. Admin role can be given by another admin in the workspace.
Admin users are not counted in Chats' "Seen" counts, but participants are. If an admin has both administrator and participant roles, they are marked as seen.
Participants have access to the workspace, but have limited visibility to the settings and have other restrictions concerning the workspace. They are not permitted to alter settings or page layouts.
Admins can edit the page layouts and add content, change workspace settings, add users (participants and other administrators), send emails and monitor the activity in the workspace.