It means approaching a potential employer, introducing yourself, and establishing rapport. Only 30 percent of all jobs are publicized through traditional channels. The remaining 70 percent are never made public. In reality, most of the best jobs are not ever advertised. In general, employers don't like to advertise.
Advertising causes a lot of extra work.
And oftentimes, employers simply don't need to advertise their job openings. Penetrating the Hidden Job Market requires an assertive attitude on the part of the job hunter. It requires the applicant to take the initiative. Because the Hidden Job Market cannot be penetrated by traditional methods, the job hunter will have to be more aggressive, by cold calling, prospecting, and networking. These approaches are dependent on personal contacts, information interviews, and referrals.