Not all positions will be advertised and this is something very important to know and understand when actively applying for jobs. Most people will tend to go to typical job search websites and submit their resume and covering letter in the hope of gaining an interview. Then their application will go into a pool of 70 or more other applicants vouching for the same position and with similar or greater skills and experience.
The hidden job market is where jobs can be found through a variety of other means than typical online applications. This is from interpersonal communication through cold calling prospective employers, networking with industry professionals via digital media platforms such as LinkedIn and potentially from undertaking volunteering with an organisation.
Tapping into the hidden job market is reachable for everyone but it does take time and effort as well as confidence. Being confident in making a call to a business and marketing your skills and experience to them and asking if there are any opportunities available. It is worth a try.