They cover ICU, hospital stay, necessary operations, medications while you are in the hospital, doctors visits, specialist visits, necessary x-rays and outpatient procedures. Injections, depends on what kind of injections. Necessary vaccinations are paid for.
What you have to pay for is if you take an ambulance, if you get medications prescribed to you and pick them up at the pharmacy and if you go to the dentist. Supplementary insurances usually cover a percentage of medications and dental work and sometimes also glasses, hearing aids and other things.