Entropy and Flux

Do you get Medicaid or Medicare?

I’ve met people who get either or both and I’m kind of confused as to who or what decides what you get and what each one covers.

According to my health reform class, Medicaid is for either people in poverty or people who receive disability, Medicare is for the elderly or people who receive disability. I would think that Medicaid then would be the default for people with disability but my mother says Medicare is?