Stop in for a cup of coffee

So what's the setup on those? Do the keep they original AM radio - or the shell, or is it always an AM/FM and use the FM as part of the recieving?
Its just a small receiver, and I think they operate independently of the stock radio. Here's an over simple one that uses the cigarette lighter. https://www.walmart.com/ip/Monster-...5035&wl11=online&wl12=987288335&wl13=&veh=sem