In the U.S., people have private health insurance plans that they buy themselves or get through their job. Different people have different insurance plans. Each doctor, dentist, etc. has certain insurance plans that they "take" (accept), and others that they don't take.

Because of this system, when you call a doctor's office to make an appointment, you have to ask "Do you take ___?"

Sometimes it's written on the doctor's website:

We take United Health Care and Emblem Health.