Rental Cars ??

I’m watching all these sailing videos on YouTube, which I don’t want to get into a discussion on the pros and cons of. All that… I just want a simple answer to a simple question if anybody happens to know any overseas Cruisers listening.. I’ve been to the Caribbean for instance ,but, I never tried to rent a car my question is this ?? How are all these foreigners renting cars and all of these different islands and countries I’ve seen it in Europe also, I know good and well these…Rental Cars ??