What does freiwillig versichert mean?

A definition of the term "freiwillig versichert", in plain English.

If you are a freelancer, or if you make over 62550€ per year, you are voluntarily insured (freiwillig versichert). This means that public health insurance companies are not forced to accept you. It also means that you can choose private health insurance. Teachers and students are also voluntarily insured.