The major difference between ham radios and the radio in your car or stereo is that ham radios cannot broadcast to the public. Hams operate at frequencies above AM radio (1.6 MHz and above), so you can’t pick up ham radio communications in your car.
In addition, ham radios can communicate over much greater distances than can traditional radios because they do not use line of sight technology; rather, ham radios send signals to bounce off the ionosphere and return to an antenna. On the other hand, they operate on much more restricted power levels than do traditional radios.
Perhaps a closer analogy to ham radios are CB radios, but ham radios have more power than do CBs, and they are also able to access larger segments of the radio frequency than can CBs. Hams can, however, often pick up CB conversations.