"Headhunters" are full-time dedicated recruitment agents hired by companies to find suitable candidates for job vacancies. They can be self-employed or work for a service provider specialised in the provision of personnel.
"HR professionals" are employees in companies who are solely concerned with finding new employees for their company.
The headhunters and HR managers you can select in your career settings are "Top Recruiter" users of the XING TalentManager.
There are other headhunters and HR managers active on XING who don’t use the XING TalentManager. These people are not included in the settings you make under "Top recruiters on XING".