Public health insurance or statutory health insurance (gesetzliche Krankenversicherung or GKV) pays for your healthcare when you need it. It's also called statutory health insurance. Public health insurance companies are called Krankenkassen.
89% of Germans have public health insurance. The rest have private health insurance instead.
Public health insurance costs a percentage of your income. If you earn more, you pay more. The cost does not depend on how healthy you are.