It's a bit more than that. Your typical home booster has an "external" antenna that captures the weak cell signal, and then the booster uses a built-in amplifier to boost that signal in it's range via a secondary "internal" antenna. Different models work with different carriers but they all follow that basic concept. Mobile units for cars run on 12vdc, home units run on 110. About the only real difference between them.So, basically an antenna?
Several years ago I had one that had a magnetic base. You plugged into your cell phone. It had a cable so you ran it out your window and stuck it to the roof of your truck.